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THE  EFFECT  OF  DRYING  SOILS  ON  THE 
WATER-SOLUBLE   CONSTITUENTS 


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A   THESIS 

PRESENTED  TO  THE  FACULTY  OF  THE  GRADUATE  SCHOOL 
OF  CORNELL  UNIVERSITY  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 


BY 


A.  F.  GU5TAFSON,  M.S. 


SEPTEMBER,  1920 


Reprinted  from  Soli  Science,  Vol.  13.  No.  3.  March,  1922. 


THE  EFFECT  OF  DRYING  SOILS  ON  THE 
WATER-SOLUBLE   CONSTITUENTS 


A   THESIS 

PRESENTED  TO  THE  FACULTY  OF  THE  GRADUATE  SCHOOL 
OF  CORNELL  UNIVERSITY  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 


BY 

A.  F.  GU5TAFSON,  M.S. 

SEPTEMBER,  1920 


Reprinted  from  Soli  Science,  Vol    13.  No.  3.  March,   1922. 


I,«>- 


Reprinted  from  Soil  Science 
Vol.  XIII,  No.  3.  March,  1922 


^^       THE  EFFECT  OF  DRYING  SOILS  ON  THE  WATER-SOLUBLE 
J  CONSTITUENTS! 

I  A.  F.  GUSTAFSON 

New  York  Slate  College  of  Agriculture  at  Cornell  University 

Received  for  publication,  May  1,  1921 
INTRODUCTION 

The  effect  of  dr>'ing  and  of  burning  soil  on  the  growth  of  crops  was  noted  in 
the  field  by  the  Roman  farmer  many  years  before  the  beginning  of  the  science 
of  soils.  At  first,  improvement  in  the  crop  was  attributed  to  the  well  known 
effect  of  drying  on  the  physical  condition  of  medium  and  fine-grained  soils; 
later,  as  chemistry  developed,  the  increased  growth  was  considered  to  be  due 
to  some  chemical  change  which  occurred  in  the  soil  during  the  process  of 
drying;  while  a  more  recent  idea  is  that  the  improvement  is  brought  about  by 
readjustment  in  the  microscopic  life  of  the  soil. 

For  several  decades  greenhouse  growers  have  practiced  heating  the  soil  to 
kill  various  plant  and  animal  enemies  of  the  crop.  In  many  instances  the 
improvement  in  growth  was  greater  than  could  have  been  affected  by  steriliza- 
tion alone,  the  rank  growth  of  stem  and  dark  green  color  of  leaf  being  par- 
ticularly noticeable.  Some  growers  have  found  it  necessary  to  withhold  a 
portion  of  the  nitrogen  usually  supplied,  to  avoid  excessive  growth  of  the 
vegetative  portion  of  the  plant  and  thus  permit  proper  fruiting. 

It  is  the  purpose  of  this  paper  to  review  the  observed  effects  of  drying  and 
heating  soils,  and  to  present  some  experimental  data  indicating  the  effect  of 
drying,  and  of  heating  at  105°C.,  on  the  amount  of  total  water-soluble  solids 
recovered  by  extraction  with  distilled  water. 

REVIEW   OF   LITERATURE 

Davy  (17)  says: 

"The  improvement  of  lands  by  burning  was  known  to  the  Romans.  It  is  mentioned  by 
Virgil  in  the  first  book  of  the  Georgics.  It  is  a  practice  still  much  in  use  in  many  parts  of 
these  islands;  the  theory  of  its  operation  has  occasioned  much  discussion,  both  amongst 
scientific  men  and  farmers.  It  rests  entirely  upon  chemical  doctrines;  and  I  trust  I  shall  be 
able  to  ofi'er  you  satisfactory  elucidations  on  the  subject." 
Also: 

"Whenclay  or  tenacious  soils  are  burnt,  ....  they  are  brought  nearer  to  a  state 
analogous  to  that  of  sands All  poor  siliceous  sands  must  be  injured  by  it  (burn- 
ing), and  here  practice  is  found  to  accord  with  the  theory." 


1  A  thesis  submitted  to  the  Faculty  of  the  Graduate  School  of  Cornell  University  in 
partial  fulfillment  of  the  requirements  for  the  Degree  of  Doctor  of  Philosophy,  September, 

1920. 

173 

SOIL  SCIENCE,    VOL.   XIU,    NO.   3  P^  i\  ''^  i   ^'  '   >  (' 


5078:^:^ 


174  -  *••'       ,  '*.•   :  :A-  t;./-GUST.vFSON 

Warington  (k)2)'(v<)rtc&igwitli  i^oUs  l^>at  Jiatl  been  dried  at  SS'C.  for  8  hours  found  that 
the  first  150  cc.  of  extract  from  7  pounds  of  dry  powdered  soil,  contained  all  the  chlorides  and 
98.8  per  cent  of  the  nitrates.  He  states  that,  if  the  soil  were  wet,  a  much  greater  volume  of 
water  would  be  required  to  leach  out  all  the  chlorides  and  nitrates  as  it  would  be  necessary 
to  displace  all  the  water  present  in  the  soil.  He  noted  that  oven-drjang  caused  a  reduc- 
tion in  quantity  of  nitrates,  that  the  decrease  was  not  so  great  when  the  soil  was  dried  slowly 
and  that,  when  air-dried  at  10°C.,  there  was  an  increase  in  nitrates. 

Frank  (24)  extracted  30  gm.  of  soil  with  2  liters  of  distilled  water,  comparing  unheated, 
air-dry  soil  with  the  same  heated  in  an  autoclave  at  100°C.  Heating  increased  the  total 
soluble  matter  in  sand  50  per  cent  and  in  the  swamp  soil  over  150  per  cent.  The  soluble 
organic  matter  was  almost  trebled  in  each  case.  Larger  crops  of  oats  and  yellow  lupines 
were  produced  on  the  heated  soils. 

Liebscher  (60)  found  that  heating  soil  with  steam  increased  the  solubility  of  phosphorus 
and  nitrogen  compounds. 

Schmoeger  (88)  heated  moor  soil  at  150  to  160°C.  for  10  hours,  with  the  result  that  the 
phosphorus  soluble  in  hydrochloric  acid  was  doubled. 

Deherain  and  Demoussy  (18)  heated  two  soils  in  an  autoclave  at  120°C.  for  1  hour.  When 
these  heated  soils  were  inoculated  with  fresh  soil,  they  produced  more  nitrate  nitrogen  and 
ammonia  than  did  the  original  soils. 

Pfeifler  and  Franke  (73)  heated  soil  under  a  pressure  of  1  atmosphere  for  3  hours.  The 
soil  so  treated  produced  a  larger  crop  of  mustard  than  the  unheated  soil  and  it  contained  a 
higher  percentage  of  nitrogen. 

On  heating  a  garden  soil  in  an  oven  at  100°C.,  on  3  successive  days,  Richter  (82)  found 
that  the  amount  of  water-soluble  organic  matter  trebled,  and  the  total  soluble  matter  almost 
doubled. 

Tacke  (100)  showed  that  a  fresh  swamp  soil  contained  very  little  water-soluble  phos- 
phorus, and  drying  at  70  to  80°C.  rendered  more  than  half  of  the  total  phosphorus  soluble 
in  water. 

Tacke  and  Immendorf  (101)  found  the  solubility  of  phosphorus  and  potassium  in  some 
swamp  soils  was  increased  by  drying  at  80°C.  In  another  experiment  they  found  heating  at 
100  and  180°C.  doubled  and  trebled,  respectively,  the  amount  of  water-soluble  phosphorus. 

Stone  and  Smith  (99)  report  that  heating  soil  improves  the  color  and  causes  an  accelera- 
tion of  growth  of  lettuce,  cucumbers  and  tomatoes  and  that  saprophitic  fungi  not  found  in 
unheated  soil  grew  profusely  on  heated  soil,  indicating  a  change  in  the  organic  matter. 

Kriiger  and  Schneidewind  (58)  showed  definitely  that  soluble  nitrogen  and  phosphorus  was 
greatly  increased  by  heating.  On  both  unmanured  soil  and  that  supplied  with  sodium 
nitrate,  the  growth  of  mustard  was  nearly  doubled  by  heating  the  soil  before  planting, 

Deitrich(  19)  heated  garden  soil  and  secured  increased  crops;  but,  curiously  enough, 
pasture  soils  did  not  respond  in  the  same  way. 

Whitney  and  Cameron  (103)  found  that  air-dried  soils,  in  general,  had  more  soluble 
phosphoric  acid,  nitric  acid,  calcium  and  potassium  than  fresh  soils,  and  that  with  few  excep- 
tions oven-dried  soils  had  still  greater  quantities  of  these  materials  in  soluble  form.  Nitric 
acid  was  most  variable. 

Card  and  Blake  (9)  report  in  each  of  two  trials,  a  decrease  in  yield  of  lettuce  due  to  sofl 
sterilization,  while  in  one  trial  radishes  gave  an  increase  where  nitrate  of  soda  was  added  to 
sterilized  soil. 

Hassenbaiimer,  Coppenratli,  and  Konig  (29)  report  that  the  solubility  of  inorganic  con- 
stituents was  increased  when  250  gm.  of  soil  and  3  liters  of  water  were  heated  together  under 
a  pressure  of  3  atmospheres  for  3  hours. 

King  (45)  reviewed  fully  the  recorded  experimental  work  on  water  extracts  of  soils  and 
extraction  with  dilute  acids.  These  reports  date  back  to  the  work  of  Grouven  in  1858  and 
include  that  of  Wunder  and  Eichhorn,  1860,  Peters,  1860,  Jarriges,  1861-1862,  Hoffman, 
1863,  Schulze,  1864,  and  Ilayden,  1865.    Nearly  all  of  these  investigators  report  potash, 


EFFECT   OF   DRYING   SOILS   ON  WATER-SOLUBLE   CONSTITUENTS  175 

lime,  magnesia,  soda,  oxide  of  iron  and  aluminum,  phosphoric,  sulfuric  and  carbonic  acids, 
chlorine,  silica  and  organic  matter  separately.  Their  results  vary  greatly  for  any  one  con- 
stituent because  of  the  wide  range  of  soils,  temperatures  and  moisture  contents  used. 

These  results  are  especially  interesting  since  several  of  them  were  obtained  by  methods 
essentially  similar  to  those  of  King,  who  used  100  gm.  of  soil  and  500  cc.  of  distilled  water. 
The  soil  was  stirred  in  a  mortar  with  enough  water  to  make  a  thick  paste  in  order  to  break 
down  all  granules,  after  which  the  remainder  of  the  500  cc.  of  water  was  added.  Then  the 
supernatant,  turbid  liquid  was  transferred  to  a  pint  Mason  jar  and,  usually  within  15  minutes, 
to  the  Pasteur-Chamberland  filter  chamber. 

Filtration  was  accomplished  by  a  pressure  of  30  to  40  pounds.  Clear  extracts  were  ob- 
tained in  5  to  20  minutes,  depending  on  the  type  of  soil,  and  the  amount  of  clay  and  fine 
silt  remaining  in  suspension  to  coat  the  walls  of  the  filters.  It  was  during  the  3  minutes 
of  active  agitation  that  the  main  part  of  actual  solution  occurred.  It  was  found  that  longer 
washing  did  not  materially  increase  the  amount  of  salts  going  into  solution.  At  first  the 
electrical-resistance  method  was  employed  for  determining  concentration  but  it  was  found 
more  accurate  to  evaporate  definite  quantides  of  the  extract,  dry  in  an  oven  and  weigh. 
NOi,  HPO4,  CI  and  SiOj  were  determined  by  methods  described  by  Whitney  and  Cameron 
(103).  Comparisons  were  made  of  the  salts  that  could  be  recovered  from  fresh  soU,  soil 
quickly  sun-dried  and  from  that  oven-dried  at  1 10°C.  Eight  soils  in  four  1-foot  sections  were 
used.  In  the  surface  foot,  of  four  soils  the  oven-dry  soil  had  more  nitrates,  while  in  the 
other  four,  the  fresh,  moist  soil  had  more;  but  in  the  second,  third,  and  fourth  sections  the 
nitrates  were  increased  108,  134  and  61  per  cent,  respectively.  In  two  of  the  eight  soils  the 
fresh  sample  showed  considerably  more  HPO4  in  the  first  section  than  the  dry  and  in  eight 
instances  in  the  other  3  feet  out  of  the  24  possible  cases  the  fresh  soil  was  slightly  higher.  In 
every  case  (except  one  in  fourth  foot),  the  dry  soil  gave  up  much  more  SO4;  for  the  eight  soils 
the  average  increase  for  the  four  sections  was  265,  310,  281  and  79  per  cent,  respectively. 
In  one  instance  only  was  the  fresh  soil  significantly  higher  in  HCOs  while  in  the  others  the 
dry  was  from  48  to  73  per  cent  higher.  Silica  was  588,  322,  237  and  236  per  cent  higher 
in  the  oven-dried  soil  in  the  four  sections.  Chlorine  was  the  only  element  that,  on  the  aver- 
age, was  recovered  in  smaller  quantity  from  the  dry  soil.  The  other  acid  radicals  ran  from 
1.26  times  as  much  nitrates  up  to  6.58  times  as  much  of  silica  in  the  dry  as  in  the  fresh  soiL 

Later,  determinations  were  made  of  potash,  lime  and  magnesia  in  the  extract  of  fresh 
and  oven-dried  soils.  In  part  II,  King  reports  good  correlation  between  quantity  of  soluble 
salts  found,  especially  HPO4,  and  crop  yields  for  the  different  soil  types  under  investigation. 

King  concluded  that  in  oven-drying  the  last  of  the  moisture,  for  a  time  at  a  temp>erature 
near  the  boiling  point,  increases  the  solubility  of  salts  and  might  be  expected  also  to  render 
the  organic  matter  more  soluble.  He  also  concluded  that  when  a  soil  dries  its  salts  are 
deposited  as  crystals  on  the  soil  particles  and  salts  within  the  granules  are  left  on  the  exterior. 
As  the  soil  is  stirred  in  water,  these  salts  go  into  solution  readily.  On  the  other  hand,  in 
a  moist  soil  the  solution  is  simply  diluted  by  adding  water  and  the  dissolved  salts  are  dis- 
seminated through  it  in  part  by  diffusion,  a  slow  process.  The  solution  from  the  dry  soil  is 
removed  from  it  before  readsorption  occurs.  Thus,  he  explains  the  recovery  of  more  soluble 
material  from  the  dry  than  the  moist  soil. 

Hilgard  (30)  considered  the  unusual  productiveness  of  desert  soils  when  properly  watered, 
due  to  an  abundant  supply  of  plant  nutrients  rendered  available  by  the  intense  heating  to 
which  these  soils  are  subjected  during  the  warm  season.  With  King  he  believed  that  the 
soluble  salts,  on  drying,  are  deposited  on  the  surface  of  the  particles  whence  they  may  be 
"readily  abstracted  by  the  first  touch  of  the  solvent  water,"  and  that  soils  retain  salts  in 
a  condition  of  purely  physical  adsorption. 

Stone  and  Monohan  (98)  noted  that  sterilizing  loam  increased  the  growth  of  soybeans 
14  per  cent,  but  that  sterilizing  in  the  same  way  decreased  the  growth  of  soybeans  in  subsoil 
57.7  per  cent.    The  subsoil  pots  showed  poor,  sickly  development. 


176  A.   F.   GUSTAFSON 

Schulze  (91)  noticed  mjurious  effects  from  sterilization  at  100  to  125*C.  for  1  hour,  in  the 
early  stages  of  growth,  but  later  these  plants  became  more  vigorous  and  produced  a  larger 
crop,  except  peas  and  mustard  on  one  soil. 

Darbishire  and  Russell  (16)  heated  soil  at  90  to  95°C.  and  obtained  very  marked  increases; 
the  wheat  yield  (grain),  from  heated  soil  was  3.5  times  as  great  as  from  unhealed,  and  spinach, 
tomato  and  verbena,  gave  over  four  times  the  yield  on  the  heated  soil.  The  second  crop, 
and  even  the  third  in  one  case,  showed  the  same  influence,  though  there  was  no  increase  in 
legumes.     Heating  to  higher  temperatures  somewhat  intensified  the  effect. 

Koch  and  Luken  (55)  heated  a  poor  sandy  soil  in  an  autoclave  for  2  hours  under  pressure 
of  two  atmospheres.  This  almost  doubled  the  total  soluble  solids,  quadrupled  the  soluble 
organic  matter,  but  increased  the  soluble  inorganic  material  only  slightly.  Even  though 
heated  and  unhealed  soils  were  fertilized  alike,  the  heated  one  produced  the  larger  crop  of 
oats.  Injurious  effects  following  heating  were  noticeable,  but  with  crops  seeded  later  in  the 
season  this  influence  was  not  great. 

Rahn  (81)  made  an  e.xtensive  study  of  the  effect  of  drying  on  soils.  After  drying  at  room 
temperature,  he  secured  markedly  increased  bacterial  activity,  the  difference  being  greater 
in  heav>'-,  rich  soils,  and  increased  growth  of  mustard. 

Pickering  (74)  heated  a  soil  at  200  C.  for  2  hours,  finding  that  2  year-old  apple  trees 
made  63  per  cent  more  growth,  produced  48  per  cent  more  leaves  containing  52  per  cent 
more  dry  matter  than  did  similar  trees  in  untreated  soil.  Heating  in  a  moist  condition  in- 
creased the  soluble  matter,  both  organic  and  mineral,  more  than  when  heated  in  the  dry 
condition.  Heating  soil  at  100  C.  in  a  closed  vessel  (75)  increased  total  soluble  matter  25 
per  cent  in  one  case  and  107  per  cent  in  another,  and  in  11  soils  an  average  increase  from 
0.052  to  0t360  per  cent  of  soluble  organic  matter  and  from  0.111  to  0.475  percent  of  total 
soluble  matter  was  secured. 

Gedroitz  (25)  found  that  sterilization  brought  about  an  increase  in  the  solubility  and 
assimilability  of  nutritive  substances. 

Russell  and  Hutchinson  (86)  report  that  heating  soil  at  98°C,  increased  the  j'ield  of  rye 
60  per  cent  and  buckwheat  31  per  cent. 

Mann  (64)  gives  a  brief  account  of  the  "Rab"  system  of  rice  growing,  viz.,  "burning  a 
mass  of  branches  of  trees  or  cow  dung  on  the  land"  where  rice  is  to  be  seeded.  He  states 
that  it  is  an  almost  universal  practice  on  the  trap  and  laterite  soils  of  western  India  and  is 
considered  essential  to  rice  culture  there.  The  surface  soil  is  heated  sufiiciently  to  change 
tlie  bacterial  flora,  increase  the  soluble  organic  matter  and  improve  the  physical  condition 
of  the  soil. 

King  (46)  treated  sand  repeatedly  with  disulfonic  acid  to  free  it  from  all  traces  of  nitric 
acid  and  organic  matter,  then  charged  it  with  potassium  nitrate,  which,  after  a  time,  was 
drained  away.  After  the  sand  dried,  50  gm.  were  washed  mth  100  cc.  of  distilled  water,  the 
mass  was  stirred  continuously  for  3  minutes,  the  solution  drained  from  the  sand  and  the 
nitric  acid  determined.  This  was  repeated  until  ten  washings  in  all  had  been  made.  Table  A 
gives  the  results  of  these  determinations. 

After  the  tenth  washing  the  sand  was  treated  with  disulfonic  acid,  as  is  the  residue  in  an 
ordinary  nitrate  determination,  and  was  shown  to  contain  0.8  mgm.  of  nitrates,  or  nearly 
three  times  the  amount  recovered  in  the  second  washing,  more  than  one-fourth  as  much  as 
recovered  in  the  first  washing. 

King  reasoned  from  this  that  each  sand  grain  "appropriated  to  itself"  a  film  of  water  with 
potassium  nitrate  in  solution  and  this  film  adhered  to  the  particle  so  closely  that  in  stirring 
after  adding  100  cc.  of  distilled  water  the  nitrate  was  given  up  by  diffusion  only  and  not  by 
forming  a  mechanical  mixture  of  the  distilled  water  with  the  film. 

Lyon  and  Bizzell  (61)  found  that  steaming  for  2  to  4  hours  under  2  atmospheres  pressure 
increased  water-soluble  ammonia,  organic  nitrogen,  nitrites  and  total  soluble  matter,  but 
lessened  the  amount  of  nitrates.  On  standing  56  to  90  days  after  heating,  there  was  a  de- 
crease in  these  soluble  materials,  except  nitrates  which  remained  constant.    Wheat  grown  in 


EFFECT  OF  DRYING   SOILS   ON  WATER-SOLUBLE  CONSTITUENTS 


177 


steamed  soils  at  first  showed  injury,  but  later  recovered  and  grew  better  than  i)lants  on  the 
unsterilized  soil. 

Two  soils  heated  for  2  hours  at  2  atmospheres  pressure  and  another  for  4  hours  (62),  were 
extracted  with  5  parts  of  water  to  1  part  of  soil.  Total  solids  and  inorganic  matter  were  in- 
creased from  two  to  six  times  by  this  heating.  All  other  constituents  except  nitrates  were 
greatly  increased  by  heating.  No  ammonia  was  found  in  any  unheated  soil  and  the  con- 
centration of  nitrates  was  decreased  by  heating  in  every  case.  Wheat  produced  a  much 
larger  crop  on  the  heated  than  on  the  unheated  soil,  and  the  same  effect  was  very  evident  in 
the  succeeding  crop  of  millet,  but  wheat  seedlings  grown  in  a  1  -1  extract  made  immediately 
after  steaming,  were  affected  unfavorably.  Diluting  the  extract  of  steamed  soil  with  distilled 
water,  3  to  1,  improved  the  growth  of  seedlings  but  diluting  the  extract  of  untreated  soil 
decreased  the  growth  of  seedlings. 

The  same  writers  (62)  report  that  soils  whose  moisture  content  was  maintained  at  about 
25  per  cent  by  adding  distilled  water,  for  periods  of  56,  82  and  90  days  after  heating,  steadily 
lost  in  total  water-soluble  material  so  that  at  the  end  of  90  days  there  was  but  slightly  more 

T.\BLE  A« 
Observed  and  computed  conceniration  of  ?iilrale  in  successive  washings  of  sand  in  distilled  water 


CONCENTRATION   OF  SOLUTION 

NXTMBER  OF  WASHING 

WATER   RETAINED    IN   SAND 

Observed 

Computed 

gm. 

p.  p.  m. 

p.  p.  m. 

1 

12.7 

35.750 

43.4551000 

2 

13.2 

3.300 

4.8969000 

3 

13.1 

0.451 

0.5710100 

4 

13.4 

0.174 

0.0661390 

5 

13.05 

0.138 

0.0078153 

6 

13.3 

0.128 

0.0009023 

7 

13.5 

0.110 

0.0001059 

8 

13.5 

0.110 

0.0000126 

9 

13.5 

0.110 

0.0000015 

10 

13.4 

0.110 

0.0000002 

than  one-fourth  as  much  soluble  material  present  as  immediately  after  heating.  Nitrates 
decreased  also,  but  in  one  soil  they  seemed  to  recover  in  part  at  the  close  of  the  period. 

In  a  more  extended  experiment  along  the  same  line,  soils  stood  34  and  39  days  after  heat- 
ing. Total  solids,  inorganic  matter  and  ammonia  nitrogen  decreased  rapidly,  while  there 
was  a  slight  increase  in  nitrates  in  the  same  time. 

Fletcher  (23)  relates  that  burning  organic  matter,  twigs  or  manure,  or  both,  greatly 
increased  the  yield  of  crops,  but  not  to  so  great  an  extent  as  did  heating  the  soil  directly  at 
200  to  230°F. 

Aitken  (1)  reports  an  instance  of  increased  productiveness  follo-ning  heating  of  the  surface 
garden  soil  by  a  "large  and  long-continued  fire." 

Howard  and  Howard  (36)  mention  the  beneficial  effects,  noted  in  parts  of  India,  of  expos- 
ing soil  to  the  strong  heat  and  light  of  the  sun  in  April  and  May. 

In  soils  kept  moist  for  various  lengths  of  time  in  open  pans,  Pickering  (76)  noted  that  the 
soluble  matter,  both  organic  and  inorganic,  increased  as  the  temperature  was  raised  from  30 
to  150''C.  The  quantity  of  soluble  matter  decreased  as  the  time  since  heating  increased, 
up  to  112  days  when  the  last  determination  was  made.     In  case  of  the  inorganic  matter  at 


*  Letters  used  for  tables  derived  from  the  literature. 


178  A.   F.   GUSTAFSON 

100°C.,  however,  there  was  an  increase  at  both  44  and  112  days.  WTien  the  soils  were  kept  in 
sealed  flasks  there  was  an  increase  after  10  days  in  every  case  except  that  of  inorganic  matter 
at  US^C.  When  stored  in  sealed  flasks  for  43  days,  the  soils  heated  at  100  and  125°C.  showed 
«li]^ht  increase  of  soluble  matter.  WTien  stored  for  1 16  days  there  was  a  gain  in  the  amount  of 
soluble  organic  matter  at  the  above  temperatures  but  a  loss  in  tlie  quantity  of  soluble  in- 
organic matter.  Storing  in  light  or  darkness  made  no  appreciable  difference.  In  the  case 
of  the  soil  that  had  been  heated  at  125°  there  was  no  difference  in  organic  matter  whether 
stored  at  15°  or  5°,  but  that  was  a  rather  marked  increase  of  inorganic  matter  for  the  lower 
temperature. 

Pickering  (77)  secured  increased  growth  of  grasses  and  non-grasses  (except  in  a  preliminary 
experiment  with  the  latter)  when  planted  in  soils  previously  heated.  The  amount  of  growth 
increased  as  higher  temperatures  were  used.  This  increased  growth  correlates  fairly  closely 
with  increase  in  soluble  material,  both  organic  and  inorganic,  resulting  from  heating. 

Hall  (26)  says,  in  speaking  of  effect  of  sterilization  of  soil,  "Approximately,  the  crop 
becomes  doubled  if  the  soil  has  been  first  heated  to  a  temperature  of  70  to  100°C.  for  2  hours," 
while  volatile  antiseptics  bring  "about  an  increase  of  30  per  cent  or  more." 

Russell  (85)  discusses  briefly  the  beneficial  effects  of  sterilization  by  heat  and  antiseptics, 
and  assigns  killing  of  the  larger  soil  organisms  which  destroy  the  beneficial  ones,  as  the 
explanation  of  the  effect  of  this  treatment. 

Dyer  (20)  states  that  commercial  vegetable  growlers  near  London  partially  sterilize  their 
greenhouse  soils  with  steam  and  if  they  use  the  ordinary  amount  of  nitrogenous  fertilizer  the 
plants  grow  so  rank  as  to  "spoil  their  bearing  capacity." 

Seaver  and  Clark  (92)  heated  soils  from  New  York,  Massachusetts  and  North  Dakota. 
They  found  that  the  soluble  matter  in  extracts  of  heated  soils  was  generally  six  to  ten  times 
as  great  as  that  from  the  same  soil  not  heated.  The  increase  varied  somewhat  with  the 
organic  content  of  the  soil,  the  temperature  to  which  it  was  heated,  and  the  period  of  heating. 

Hinson  and  Jenkms  (31)  state  that  tobacco  plants  in  steamed  soils  start  quicker  and 
grow  faster  than  in  unheated  soil.  They  think  this  accelerated  growth  due  to  warming  the 
soil,  possible  solvent  action  of  the  steam  on  the  plant-food,  but  surely,  in  part,  to  change  in 
the  "microbe  life  in  the  soil." 

In  Kentucky,  it  is  a  common  practice  among  tobacco  growers  to  heat  or  bum  the  soil  of  the 
tobacco  beds  to  kill  weed  seeds  and  disease. 

Nagoaka  (69)  reports  a  material  increase  in  solubility  of  phosphorus  in  dilute  acids  after 
heating  the  soil.  He  found  autoclave  heating  had  greater  effect  on  solubility  than  other 
methods. 

Peterson  (72)  heated  wavellite  and  found  that  it  increased  the  quantity  of  phosphorus 
soluble  in  0.2  N  nitric  acid  from  4.12  per  cent  of  the  total  phosphorus,  in  unheated  material, 
to  54.9  per  cent  in  wavellite  heated  to  160°C.,  49.0  per  cent  at  200°,  and  98.7  per  cent  at 
240°C.  He  noted  little  effect  on  soil  at*100°C.  but  at  200°,  after  a  five-hour  treatment,  there 
was  a  marked  increase  in  solubility  of  phosphorus. 

Ritter  (83)  exj)erimented  along  the  same  lines  as  Rahn  and  found  that  drying  increased 
bacterial  activity,  and  with  less  effect  on  light  than  on  heavy  soils. 

Fischer  (22)  comments  on  the  work  of  Rahn  and  Ritter,  but  holds  the  chemical  factor 
more  important  than  the  bacterial.  He  attaches  much  importance  to  oxidation  since  drying 
increases  the  amount  of  nitrates,  even  though  it  kills  nitrifying  organisms;  also  credits  colloids 
and  surface  tension  with  playing  important  rdles. 

Schreiner  and  Lathrop  (90)  in  studying  the  chemistry  of  steam-heated  soils  made  1  to  4 
extracts.  Many  organic  compounds  were  found  in  heated  soil  that  were  not  isolated  from 
fresh  soil.  Dihydro.xystearic  acid  was  increased  when  present  in  the  fresh  soil  and  produced 
when  not  present.  Seedlings  were  grown  in  the  extracts  for  10-  and  15-day  periods;  extracts 
from  heated  soil  depressed  growths.     Heating  increased  acidity. 

Skalskii  (94)  found  that  sterilizing  with  chloroform  and  with  heat  increased  the  yield  of 
crops  by  converting  phosphoric  acid  and  nitrogen  into  available  forms. 


EFFECT   OF  DRYING   SOILS   ON   WATER-SOLUBLE   CONSTITUENTS  179 


Stone  and  associates  (97)  report  greatly  increased  bacterial  develoi)ment  in  extracts  from 
soils  rich  in  organic  matter,  which  had  been  heated  previously,  while  it  was  retarded  in 
extracts  from  [)oor  soils.  They  consider  the  chemical  factor  most  important  in  accounting 
for  the  elTect  of  heating. 

Leather  (59)  in  studying  the  nitrate  content  of  soils,  at  Tusa  states  that  drying  in  the 
sun  effected  an  increase  as  great  as  400  per  cent. 

Seaver  and  Clark  (93)  found  an  increase  in  total  soluble  solids,  organic  matter,  inorganic 
matter  and  total  nitrogen,  in  soil  when  heated  at  90°C.  and  still  greater  increases  at  120, 
150  and  170°C.  Plant  growth  was  accelerated  by  heating  at  90  and  120°C.  but  retarded 
at  the  higher  temperatures,  which,  however,  increased  the  growth  of  fungi.  They  noted  that 
heating  increased  acidity  and  suggest  that  this  may  account  for  the  better  growth  of  plants 
such  as  blueberry  on  "  burned  over"  soils. 

Lyon  and  Bizzell  (63)  have  shown  that  when  a  soil  has  been  heated  to  complete  sterility 
by  steaming  and  subsequently  maintained  at  a  moisture  content  of  25  per  cent  of  its  dry 
weight,  the  total  solids  decrease  rapidly,  as  shown  in  table  B. 

TABLE  B 
Effect  of  standing  on  the  water-soluble  constituents  of  heated  soils 


Soil  1 ,  Dunkirk  clay  loam 

Freshly  heated 

5  weeks  after  heating 

14  weeks  after  heating 

Soil  2,  Volusia  silt  loam 

Freshly  heated 

5  weeks  after  heating 

14  weeks  after  heating 

Soil  3,  Dunkirk  clay  loam  with  extra  organic  matter 

Freshly  heated 

5  weeks  after  heating 

10  weeks  after  heating 

19  week  safter  heating 


PARTS  PER  MILLION  OF  DRY  SOIL 


Total  solids 


3334 
2161 
1740 


3020 
2098 
1801 


7194 
3288 
2719 
2173 


Nitrates 


64.9 
61.9 
69.0 


175.1 
178.2 
191.5 


234.0 
306.0 
282.5 
160.0 


Ammonia 
nitrogen 


33.0 
41.5 
51.0 


33.5 
36.5 
45.0 


84.1 

79.5 

96.0 

111.0 


The  nitrates  have  been  affected  but  slightly,  except  in  Dunkirk  clay  loam  with  extra 
organic  matter,  where  there  was  an  increase  during  first  5  weeks,  but  a  rapid  decline  later, 
and,  in  general,  an  increase  in  ammonia  nitrogen. 

In  another  experiment,  freshly  heated  soil  had  1010  parts  per  million  of  total  soluble  solids 
and  246  parts  per  million  of  inorganic,  while  after  3  months  the  corresponding  amounts  are 
590  parts  per  million  of  total  soluble  solids,  and  126  parts  per  million  of  inorganic.  When 
aerated  during  the  3-month  period,  there  is  a  further  decrease  to  434  and  120  parts  per  million, 
respectively. 

Russell  and  Petherbridge  (87)  state  that  plants  grown  on  soils  heated  at  100°C.,  in  com- 
parison with  unheated  soils,  have  larger  leaves  of  deeper  green  color  and  stouter  stems,  they 
flower  earlier  and  more  abundantly,  the  fruiting  is  more  prolific,  and  they  contain  a  higher 
percentage  of  nitrogen  and  sometimes  phosphoric  acid  in  their  dry  matter. 

Konig,  Hasenbaumer  and  Glenk  (56)  heated  soil  at  95°C.  in  a  vacuum,  which,  in  most 
cases  contained  markedly  more  water-soluble  organic  matter  as  well  as  total  soluble  solids 


180  A.   F.   GUSTAFSON 

than  did  unhealed  soils.  Heating  at  150°C.  still  furtlier  increased  the  solubility  of  both 
organic  and  mineral  matter.  In  most  comparisons,  heating  increased  the  amount  of  water- 
soluble  phosphorus,  yet  a  few  gave  slightly  less.  Pot  experiments  with  oats  showed  that 
heating  in  a  vacuum  at  95  to  98''C.  increased  the  growth. 

Wilson  (106)  secured  slightly  increased  growth  of  plants  in  soil  heated  at  95°C.,  but 
retardation  at  higher  temperatures,  the  effect  varying  with  the  kind  of  soil  and  nature  of 
crop  grown. 

Buddin  (8)  found  the  nitrate  content,  immediately  after  drying  in  a  thin  layer  in  labora- 
tory for  24  hours,  unafifected,  but  reducing  the  moisture  content  further  during  46  hours 
did  increase  the  nitrate  content  slightly.  When  the  dried  soils  were  remoistened  and  in- 
cubated for  40  days,  there  was  a  marked  increase  in  nitrates;  untreated  moist  soil  36  parts 
per  million,  soil  spread  in  gallery  46,  and  in  glass-house  53.5  parts  per  million. 

King  (48)  relates  that  the  residents  of  northern  China  build  flues  ("Kangs")  of  sun-dried 
bricks  made  of  "soil  or  subsoil  mixed  with  short  straw  or  chaff."  After  two  to  four  years' 
use,  these  flues  become  defective,  so  that  they  must  be  replaced.  When  removed  the  bricks 
are  finely  pulverized  and  used  as  fertilizer,  being  planted  in  hills  with  the  seed.  The  soil 
while  used  as  a  flue  has  become  thoroughly  air-dry  and  on  the  inside  of  tlie  flue,  undoubtedly, 
much  of  it  has  at  times  been  freed  of  uncombined  water.  During  this  long-continued  drjdng, 
the  plant  nutrients  have  been  rendered  more  available  and  this  fact  is  made  use  of  by  the 
Chinese  farmer.  King  (47)  suggests  "absorption  of  the  products  of  combustion"  by  the 
"brick"  as  an  additional  factor  in  giving  tliem  value  as  fertilizer. 

Kellej'  and  McGeorgc  (40)  revievs-  briefly  the  history-  of  burning  soils.  There  are,  in 
Hawaii,  large  areas  of  heavy  soil  which  do  not,  when  first  plowed,  produce  satisfactory  crops. 
It  requires  several  months  of  cultivation  before  crops  thrive.  It  has  been  noticed  that  on 
small  spots  where  brush  has  been  burned  cotton  grows  exceptionally  well.  It  is  suggested 
that  this  effect  may  be  due  to  heating  the  soil  rather  than  to  the  soluble  oxides  of  phosphorus, 
potassium,  calcium  and  magnesium  in  the  ash,  since  fertilizers  do  not  produce  such  beneficial 
results. 

They  report  results  of  analyses  of  the  1 : 5  water-extract  of  a  brown  ferruginous  clay  soil 
and  its  subsoil,  and  a  similar  type  which  had  been  plowed  and  was  growing  pineapples. 
Determinations  were  made  on  fresh,  air-dried  and  oven-dried  samples,  extracted  respectively 
for  1  hour,  24  hours  and  7  days.  Phosphoric  acid  (P2O.O  was  ahvaj^s  highest  in  the  oven-dried 
soil,  manganese  oxide  (Mnj04)  always  higher  in  air-dried  than  in  fresh  soil  (not  determined  in 
oven-dried  soil).  Lime  (CaO)  was  highest  in  the  oven-dried  soil  in  three  of  nine  comparisons 
only.  Magnesia  (MgO)  varied,  in  some  samples  higher  in  the  air-dried.  Sulfuric  acid 
(SOs)  was  highest  in  the  fresh  soil  of  tener  than  in  either  of  the  others,  and  potash  was  highest 
in  the  air-dried  soil  (with  one  exception)  in  the  two  surface  soils,  while  in  the  subsoil  the 
fresh  soil  held  first  place. 

When  all  the  comparable  data  are  considered  we  see  that  in  three  cases  the  fresh  soil  was 
highest  in  total  soluble  solids,  in  three  cases  the  air-dried  and  in  the  other  three  cases  the 
oven-dried  soil  stood  first.  So  no  conclusion  as  to  the  effect  of  heating  on  total  soluble  salts 
can  be  drawn  from  these  figures. 

In  general,  extracting  for  24  hours  or  for  7  days  gave  but  slightly  higher  results  than  ex- 
tracting for  1  hour,  except  in  the  case  of  phosphorus  which  increased  in  solubility  with  longer 
extraction.  In  two  out  of  eight  trials,  heating  at  100°C.  increased  the  nitrate  content;  in 
four  soils  it  was  decreased  while  in  the  other  two  there  was  no  change.  As  the  soil  was 
raised  to  higher  temperatures,  150  to  200  and  250  nitrates  decreased  rapidly  until  almost 
none  was  recovered  at  the  highest  temperature. 

These  investigators  think  both  chemical  and  physical  factors  enter  into  an  explanation  of 
the  effect  of  drying  on  the  soluble  constituents  of  soils,  but  that  "the  most  important  set  of 
factors  affecting  the  solubility  of  inorganic  soil  constituents  are  physical  in  nature.  Also 
that  the  physical  factors  act  through  the  effect  of  changes  in  soil  moisture  on  the  physical 
properties  of  the  soil."     "The  conditions  conducive  to  the  formation  of  a  colloidal  state  and 


EFFECT  OF  DRYING   SOILS   ON   WATER-SOLUBLE  CONSTITUENTS  181 

the  subsequent  relation  of  heat  to  the  destruction  of  this  colloid  are  two  of  the  most  im- 
portant of  these  factors."  When  soil  contains  some  capillar}'  or  film  water  this  moisture  is 
distributed  about  the  particles  as  a  thin  film  varjang  in  thickness  with  the  quantity  of  water 
present  in  any  given  soil.  It  is  stated  that  tlie  moisture  film  in  air-dry  soils  is  held  with  a 
force  equal  to  10,000  atmospheres  and  that  under  such  conditions  "the  concentration  of  film 
water  with  reference  to  the  mineral  matter  should  be  much  greater  than  that  of  the  free 
or  capillary  water  in  tlie  soil."  They  hold  that  air-dried  soils  should,  and  their  results  are 
claimed  to,  show  least  solubility. 

The  films  with  organic  and  inorganic  matter  in  solution  may  be  looked  upon  as  colloidal 
in  nature.  Upon  heating  to  100°C.  alteration  in  the  film  occurs  through  evaporation  and  by 
partial  dehj-dration  of  the  colloids,  destroying  the  pressure  by  which  the  film  was  i)reviously 
held  around  the  particles.  During  evaporation  the  concentration  of  the  soil  moisture  would 
increase  to  the  saturation  point,  after  which  mineral  matter  would  be  deposited  with  further 
evaporation. 

The  solution  obtained  upon  adding  water  to  oven-dried  soil  should  be  of  greater  con- 
centration than  that  from  air-dried  soil.  With  water  films  absent  and  the  colloids  altered, 
the  water  has  more  ready  access  to  the  soil  particles.  They  found  some  mineral  constituents 
more  soluble  at  250°C.  than  at  100°C.  and  think  it  due  to  "more  complete  elimination  of 
soil  moisture  and  especially  the  water  of  chemical  combination." 

Hulett  and  Allen  (37)  showed  that  the  concentration  of  the  solution  in  equilibrium  with 
a  curved  surface  is  greater  than  that  in  equilibrium  with  a  plane  surface  and  that  gypsum  is 
most  soluble  in  water  at  40°C.    Above  80°C.  it  is  less  soluble  than  at  0°C. 

McGeorge  (66)  reports  further  results  of  heating  soils  in  sunlight,  in  an  oven  for  2  hours 
at  80,  110  and  165°C.,  and  in  an  autoclave  for  1  hour  at  10  pounds  pressure.  Onions  and 
cowpeas  showed  detrimental  effects  while  millet  show^ed  increased  vigor  with  the  higher 
temperature  of  sterilization.     Heating  gave  better  results  than  volatile  antiseptics. 

Ehrenberg  (21)  speaks  of  the  old  custom  of  using  as  fertilizer  old  garden  walls  made  of 
soil  and  says  that  many  soil  workers  have  noted  an  improvement  as  the  result  of  a  soil  drying 
out.     He  thinks  soils  rich  in  organic  matter,  only,  are  affected  materially  by  drying. 

Hall  (27)  allowed  eight  pots  of  similarly  treated  Dunkirk  clay  loam  to  dry  from  October  19 
to  March  1.  At  this  time  the  moisture  content  of  four  pots  was  brought  up  to  20  per  cent 
and  held  there  until  April  12.  The  other  four  continued  to  dry  until  JSIarch  19,  at  which 
time  the  moisture  content  was  1.8  per  cent.  The  first  four  pots  had  an  average  of  847  parts 
per  million  (of  dry  soil)  of  total  soluble  solids  and  5.18  parts  per  million  of  nitrates,  while  the 
average  for  the  four  air-dry  soils  was  1303  parts  per  million  of  total  salts  and  324  parts  per 
million  of  nitrates,  a  marked  increase  due  to  drying.  In  October,  a  sample  of  the  soil  was 
dried.  In  IMarch  it  had  1628  parts  per  million  of  total  soluble-matter  and  397  parts  per 
million  of  nitrates.  A  sample  of  the  original  soil  bottled  at  12.2  per  cent  moisture  in  October 
had  in  March  1459  parts  per  million  total  salts  and  495  parts  per  million  of  nitrates.  This 
shows  that  nitrification  had  been  active  as  in  the  soil  which  dried  to  March  1 . 

Klein  (53)  conducted  experiments  with  Dunkirk  clay  loam  (a)  low  in  organic  matter  and 
(b)  well  supplied  with  organic  matter,  this  being  timothy  sod  which  had  been  piled  up  and 
allowed  to  decay.  Keeping  soil  a  at  15,  20,  25  and  30  per  cent  moisture  and  b  at  these  mois- 
ture contents  with  an  additional  sample  at  40  per  cent,  gave  an  increase  in  growth  of  wheat 
on  a  with  a  decrease  in  moisture,  and  the  same  general  relation  held  for  b  except  that  the  soil 
with  40  per  cent  moisture  gave  practically  the  same  yield  as  that  with  15  per  cent.  There  is 
no  important  difference  in  the  yield  of  buckwheat  following  the  wheat.  Soil  a,  unplanted, 
contained  more  total  soluble  solids  with  the  lower  moisture  contents,  while  soil  b  showed  an 
increase  in  total  soluble  solids  with  an  increase  in  the  water  content.  Nitrates  decreased 
wath  the  lowering  of  the  water  content.  Difference  in  water  content  had  no  effect  on  solu- 
bility of  potassium,  calcium  and  phosphorus  in  this  soil.  Air-drj-ing  reduced  the  nitrates, 
but  when  later  brought  up  to  and  kept  at  optimum  moisture  content  for  various  periods 
greater  than  16  days,  the  nitrates  increased  materially.  The  nitrifying  power  and  power  to 
produce  carbon  dioxide  is,  in  general,  affected  in  the  same  way. 


182  A.   F.    GUSTAFSON 

Wilson  (105)  found  that  heating  at  60  to  ISO'C.  for  2  hours  increased  the  amount  of  soluble 
matter  and  changed  the  physical  condition  so  that  its  water-holding  capacity  was  affected. 
lie  accounts  for  increased  productivity  on  these  grounds. 

Huck  (7)  reports  results  of  a  study  on  the  effect  of  heat  on  soils,  by  Mann  who  found  the 
water-soluble  constituents  increased  with  the  rise  in  temperature  to  which  the  soil  was 
heated.  He  notes  greater  growth  of  rice  seedlings  immediately  after  heating,  quite  the  reverse 
of  liis  experience  with  other  plants,  which  may  be  due  to  the  ability  of  the  rice  seedling  to 
withstand  any  harmful  effects  of,  or  to  use  in  growth,  the  ammonia  which  many  hold  to  be 
a  result  of  heating. 

The  work  of  Kelley  and  Thompson  (41)  shows  that  nitrates  undergo  decomposition, 
gradually  disappearing  as  the  temperature  is  raised.  Only  slight  decomposition  took  place 
at  100°C.  Steam  heating  at  2  atmospheres  produced  effects  similar  to  those  resulting  from 
heating  at  150°C.  without  pressure. 

Houyoucos  (5)  heated  sandy  loam,  loam,  clay  and  peat  at  15  atmospheres  pressure  in  an 
autoclave  for  three  hours,  thereby  increasing  the  water-soluble  material,  as  shown  by  the 
depression  of  the  freezing  point,  respertivelj%  75,  vSO,  190  and  333  per  cent. 

In  e.Kplanation  of  the  effect  of  heat,  he  points  out  that  water  films  in  intimate  contact 
with  the  soil  particles  are  more  concentrated  than  capillary  or  interstitial  water,  due  to  the 
slowness  of  diffusion.  If  only  the  capillary  water  is  extracted,  the  quantity  of  soluble  matter 
recovered  would  be  less  than  the  total  actually  in  solution  in  the  soil  moisture.  He  suggests 
that  adsorption  may  account  for  a  higher  concentration  at  the  immediate  surface  of  the  par- 
ticles than  in  the  bulk  of  the  solution.  Furthermore,  there  is  wide  variation  in  the  solubility 
of  the  minerals  composing  the  soil  and  because  of  the  extremely  slow  rate  of  diffusion,  different 
mineral  particles  would  be  enveloped  by  films  of  varied  concentration.  This,  too,  would 
interfere  with  recovering  from  moist  soil  all  of  the  soluble  material. 

Allen  and  Bonazzi  (2)  quote  Stevens  and  Withers  showing  "only  about  40  per  cent  of  the 
citrates  were  recovered  by  1:3  extraction  when  small  quantities  were  added  and  more  than 
twice  this  amount  when  larger  quantities  were  added."  Allen  and  Bonazzi  recovered  in  the 
■first  extraction  (1:5  with  100  gm.  of  soil)  from  65.9  to  83.9  per  cent  of  the  nitrate  added,  or 
as  an  average  of  ten  results  reported,  77.4  per  cent. 

Potter  and  Snyder  (78)  report  a  recovery  of  93  to  97  per  cent  of  the  nitrate  added  at  the 
rate  of  3  parts  per  million  of  soil  (phenoldisulfonic  acid  method). 

These  authors  (79)  report  complete  extraction  of  nitrates  when  1  part  of  soil  is  shaken  with 
2  parts  of  water  for  30  minutes  (aluminum  reduction  method). 

Johnson  (38)  reports  preliminary  results,  showing  that  heating  increased  the  solubility  of 
minerals  and  the  growth  of  plants.  Heating  to  250°C.  produced  more  water-extractable 
substance  than  lower  temperatures. 

Skalskij  (95)  in  studying  methods  of  sterilization  heated  soil  in  an  autoclave  for  1  hour 
at  2.5  atmospheres.  Plants  in  this  soil  grew  as  well  as  those  in  soil  receiving  complete  ferti- 
lization, the  number  of  bacteria  was  greater  than  in  the  untreated  soil,  the  inoculation  coming 
from  the  air.  The  improved  fertility  was  due  to  a  large  increase  in  the  soluble  phosphorus, 
from  47  to  121  per  cent,  and  while  the  soluble  nitrogen  content  was  not  affected  by  heating, 
the  dark  green  color  clearly  showed  an  increase  in  the  available  nitrogen. 
Connor  (15)  reports  a  reduction  in  acidity  as  a  result  of  heating. 

Coleman,  Lint  and  Kopeloff  (14)  found  tliat  the  soluble  solids  recovered  by  1 :4  extraction 
•of  a  moist  Penn  clay  loam  soil  (25  per  cent  water  on  the  dry  basis)  after  intermittent  partial 
sterilization  at  82°C.  for  1  hour  on  each  of  5  consecutive  days,  was  increased  46  per  cent,  but 
the  amount  of  soluble  salts  was  not  appreciably  increased  after  the  first  day's  heating. 
The  air-dry  soil  (4.5  per  cent  moisture)  when  similarly  treated  showed  no  increase  in  water- 
soluble  solids.  Sterilization  by  moist  heat  at  120°C.  for  15  minutes  at  15  pounds  pressure 
increased  the  water-soluble  solids  recovered  0.0220  to  0.1805  gm.,  an  amount  8.2  times  as 
great  as  that  recovered  from  the  original  soil.  It  should  be  noted  also  that  volatile  antiseptics 
.applied  as  vapor  in  a  partial  vacuum,  increased  the  water-soluble  solids  in  air-dry  soil  22  per 


EFFECT   OF  DRYING   SOILS   ON   WATER-SOLUBLE  CONSTITUENTS  183 

cent  and  25  per  cent  in  the  moist  soil.    When  the  volatile  antiseptics  are  applied  with  heat 
(82°C.)  and  pressure,  the  amount  of  soluble  solids  in  moist  soil  is  increased  25  per  cent. 

Christensen  (10)  noted  that  air-dry  soil  had  its  power  to  liberate  acid  from  calcium  acetate 
considerably  increased  as  compared  with  that  of  fresh  moist  soil. 

Koch  (54)  determined  the  effect  of  sterilization  on  the  concentration  of  the  soil  solution 
by  means  of  the  freezing-point  method.  Concentration  was  increased  more  in  the  heavy 
soils.  Steaming  was  more  effective  than  sterilizing  with  formalin.  Using  formalin  1:50 
and  steaming  at  10  pounds  pressure  increased  the  concentration  of  the  soil  solution  more 
than  any  other  metliod  used,  in  fact  to  three  times  the  original  concentration.  In  Sassafras 
and  Penn  loams  it  was  increased,  respectively,  0.24  and  0.3  atmospheres.  Sterilization  by 
the  so-caUed  "commercial"  methods  increased  the  concentration  of  the  soil  solution,  varying 
with  soil  and  method  of  sterilization.  Heating  with  steam  at  10  pounds  pressure  for  1  hour 
increased  tlie  concentration  of  the  soil  solution  0.56  atmosphere  in  a  loam  soil;  with  a  Norfolk 
sand  tlie  increase  was  but  one-fourth  as  great. 

Stewart  (96)  studied  water  extracts  of  thirteen  soils,  of  two  distinct  types  both  planted  and 
fallow,  finding  as  did  King  (44)  that  "poor"  soils  yielded  extracts  containing  solids  less  sol- 
uble than  solids  in  extracts  from  "rich"  soils. 

Hartwell  and  Pember  (28)  while  investigating  the  effect  of  aluminum  on  barley  and  rye, 
compared  unheated  acid  soil  with  samples  heated  at  100,  260,  360,  and  420°C.  The  lime 
requirement  was  markedly  reduced  by  heating  and  the  reduction  increased  somewhat  with 
the  temperature.  The  weight  of  green  tops  of  rye  was  reduced  by  heating  except  that 
heating  at  420°C.  caused  no  difference  in  yield.  The  yield  of  green  barley  tops  was  decreased 
at  both  100  and  260°C.  but  increased  at  both  of  the  higher  temperatures. 

Potter  and  Snyder  (80)  state  that  "the  amount  of  ammonia  was  increased  by  all  the  heat 
treatments,  the  higher  temperatures  to  which  the  soils  were  heated  giving  in  general  greater 
increases;"  also  that  dry  heating  at  100°C.  did  not  materially  affect  nitrates,  but  at  10  pounds 
pressure  in  an  autoclave  for  9  hours,  nitrates  were  markedly  increased  while  a  temperature 
of  200°C.  caused  an  almost  total  disappearance  of  nitrates. 

Johnson  (39)  heated  soil  at  250°C.  The  yield  of  tobacco  was  increased  571  per  cent 
on  muck,  473  per  cent  on  Waukesha  silt  loam,  150  per  cent  on  clay,  96  per  cent  on  fine  sandy 
loam  and  62  per  cent  on  virgin  sandy  loam.  A  single  heating  gave  a  larger  yield  than  did 
heating  two  to  eight  times  at  115°C.  He  found,  also,  enormous  increases  in  concentration 
of  the  soil  extract,  as  shown  by  freezing-point  determinations.  Heating  at  250°C.  caused 
the  highest  concentration. 

He  classifies  under  eight  heads  the  published  theories  explaining  the  effect  of  sterilizing 
soils  on  plant  growth,  three  of  which  have  some  bearing  on  the  problem  in  hand;  (a)  "Modi- 
fied organic  compounds"  as  already  mentioned  from  Schreiner  and  Lathrop  (90).  {b) 
"Modified  inorganic  soil  compounds."  This  theory  is  supported  by  many  investigations 
which  show  that  an  increase  in  inorganic  plant  nutrients  occurs  on  heating  soUs.  (c)  "Physi- 
cal theories."  The  author  says  the  physical  "theories  are  not  subscribed  to  by  any  author 
in  particular  at  the  present  time,  although  it  was  quite  generally  believed  at  one  time  that 
aU  the  benefit  derived  from  burning  the  soil  was  due  to  purely  physical  changes.  Some  of 
the  physical  factors  which  play  a  part  in  soil  fertility  are,  however,  coming  to  be  regarded 
as  very  influential  in  conjunction  with  chemical  factors." 

Beaumont  (3)  showed  that  drying  soil  caused  a  decrease  in  the  amount  going  into  suspen- 
sion in  distilled  water  or  4  per  cent  ammonia.  Oven-drying  soils  and  then  putting  them  under 
water  logged  conditions  increased  the  quantity  of  iron  compounds  soluble  in  dilute  hydro- 
chloric acid.  He  states,  also,  that  "sterilization  checked  the  formation  of  this  easily  soluble 
colloidal  material." 

Noyes  (70)  while  working  with  adsorption  of  different  radicals  by  soils  and  decaying  leaves 
detected  no  adsorption  of  nitrates.  He  holds  "nitrates  are  completely  recovered  from  soil 
in  one  extraction  by  water,  and  nitrates  added  to  soil  are  completely  recovered  in  addition 
to  those  present  in  the  soil."  He  noted  also  that  the  lime  requirement  of  a  residual  limestone 
soil  was  higher  when  not  heated  than  when  evaporation  is  carried  on  in  the  usual  way. 


184  A.   F.    GUSTAFSON 

Robinson  (84)  states  that  the  lime  requirement  of  soils,  as  shown  by  the  Veitch  method, 
is  afifected  by  (a)  "the  temperature  at  which  evaporation  is  made,"  (b)  continued  heating 
after  soil  is  dehydrated,  (c)  length  of  time  during  which  treated  and  dried  soil  is  in  contact 
with  water,  and  (J)  the  source  of  heat,  such  as  steam  or  sand  bath  or  hot  plate. 

An  enormous  amount  of  interesting  work  on  the  soluble-solid  content  of  soils  under  many 
different  conditions  of  cropping  is  reported  by  King  (42,  43,  44,  46),  King  and  Jeffery  (49), 
King  and  Whitson  (50,  51,  52)  and  Whitson  (104). 

The  literature  of  drying,  heating  and  sterilizing  soil  has  been  quite  extensively  reviewed 
by  Lyon  and  Bizzell  (62)  and  (63),  Schreiner  and  Lathrop  (90),  Kelley  and  McGeorge  (40), 
Klein  (53),  Hall  (27),  Kopeloff  and  Coleman  (57),  Stewart  (96),  Beaumont  (3)  and  Johnson 
(39). 

SUMMARY  OF   LITERATURE 

1.  Heating  soil  in  various  ways  for  its  beneficial  effect  on  crops  is  an  ancient 
practice. 

2.  For  several  decades  past,  commercial  greenhouse  men  have  sterilized  the 
soil  used,  to  kill  detrimental  organisms,  and  have  noted  beneficial  results 
other  than  from  sterilization,  particularly  increased  growth  of  leaves  and  stems. 

3.  Much  careful  experimental  work  on  heating  and  drying  soils  has  been 
reported,  both  before  soil  organisms  were  recognized,  and  in  connection  with 
soil-biology  studies,  which  shows  that  drying  and  heating  soil  at  100°C.,  or 
higher,  increases  its  productiveness,  even  though  germination  may  be  retarded 
and  early  growth  depressed. 

4.  The  literature  shows  that  the  quantity  of  soluble  mineral  and  organic 
constituents  recovered  by  extraction  with  distilled  water  is  increased  by 
heating.  The  increase  bears  some  relationship  to  the  temperature  of  heating, 
the  maximum  of  soluble  constituents  being  found  at  about  250°C.,  above 
which  the  total  salts  recovered  decreases. 

5.  Investigators  are  not  in  general  agreement  as  to  the  effect  on  nitrates  of 
heating  at  100°C.  Many  workers  note  a  decrease  as  the  temperature  is 
further  raised  and  almost  total  disappearance  of  nitrates  at  250°C. 

6.  Soil  workers  are  not  a  unit  as  to  the  cause  of  the  increase  in  soluble 
material  due  to  drying  and  heating.  Some  hold  the  effect  of  heating  to  be 
largely  physical;  others  that  it  is  mainly  chemical,  and  still  others  lay  most 
stress  on  the  biological  phase.  Nearly  all  admit  that  the  physical  is  usually 
a  factor  and  others  add  colloids  as  a  physio-chemical  factor. 

7.  There  is  wide  variance  of  opinion  as  to  the  degree  to  which  nitrates  are 
recovered  by  one  or  more  extractions. 

EXPERIMENTAL  WORK 

Introduction 

While  the  literature  shows  that  an  enormous  amount  of  work  has  been 
done  on  the  effect  of  heating  at  a  wide  range  of  temperatures  and  under  varied 
moisture  contents  on  the  amount  of  soluble  constituents  of  soils,  it  was  con- 
sidered desirable  to  study  the  effect  of  drying  at  105°C.  for  8  hours,  the  ordinary 
method  of  driving  of  so-called  hygroscopic  moisture,  on  the  total  soluble  solids 
that  may  be  recovered  by  1 : 5  extraction  with  distilled  water. 


EFFECT   OF   DRYING   SOILS   ON   WATER-SOLUBLE   CONSTITUENTS  185 

Method  of  collecting  soil 

The  surface  vegetation  was  removed  and  the  surface  of  the  soil  leveled.  Steel  tubes  of 
2 J  inches  inside  diameter  at  the  cutting  edge  and  2|  inches  above  it  were  used.  A  block  of 
wood  was  placed  on  the  tube  which  was  then  driven  into  the  soil  with  a  sledge  hammer  to  a 
depth  of  8  inches.  The  soil  within  the  tube  constituted  the  "tube"  surface  sample.  Heavy 
paper  held  in  place  by  rubber  bands  was  immediately  placed  over  each  end  of  the  tube  to 
reduce  evaporation  and  aeration. 

A  sample  was  then  collected  from  immediately  around  the  tube  with  a  Ij-inch  auger  to 
the  same  depth.  This  was  immediately  placed  in  a  2-quart  Mason  jar  with  a  minimum  of 
evaporation  and  aeration.     This  was  the  "auger"  surface  sample. 

The  hole  was  enlarged  and  dug  out  with  a  spade  to  a  depth  of  12  inches  and  the  soil  from  8 
to  12  inches  discarded.  The  tube  was  driven  down  from  12  to  20  inches  and  protected  as 
before.  This  stratum  12  to  20  inches  constitutes  the  "tube"  subsurface  sample.  The 
"auger"  sample  was  collected  and  sealed  as  before.  All  samples  were  taken  to  the  laboratory. 
The  paper  cap  at  the  top  of  the  steel  tubes  was  removed  and  melted  paraffin  poured  on  so  as 
to  seal  it.  When  the  paraffin  had  solidified,  the  tubes  were  inverted,  a  portion  of  the  soil 
removed  and  tlie  tube  sealed  as  above.  Both  tubes  and  jars  were  properly  labeled  and  placed 
in  a  refrigerator,  at  a  temperature  of  8  to  12°C.  in  order  to  keep  the  soil  as  nearly  in  its 
original  condition  as  possible  by  minimizing  biological  activity. 

All  soil  samples  were  collected  and  treated  in  this  way. 

General  procedure 

Duplicate  100-gm.  samples  were  weighed  into  aluminum  dishes  of  known  weight  and  placed 
in  an  electric  oven  at  a  temperature  of  about  105°C.  for  8  hours  to  determine  the  total  mois- 
ture. After  these  had  been  weighed,  water-free  soil  from  another  dish  was  added  to  each 
to  make  exactly  100  gm.  of  water-free  soil  for  the  determination  of  total  soluble  salts  and 
nitrates. 

Lyon  and  Bizzell  (63)  have  shown  that  aerating  after  heating  has  a  marked  influence  on 
the  disappearance  of  total  soluble  solids.  For  that  reason,  all  soils  both  before  and  after 
heating  were  kept  in  closed  containers  to  reduce  aeration  to  a  minimum. 

The  percentage  of  moisture  in  the  fresh  soil  was  calculated  on  the  basis  of  water-free  soil 
as  100  per  cent.  The  method  of  obtaining  a  quantity  of  moist  soil  precisely  equivalent,  to 
100  gm.  of  water-free  soil,  was  to  add  to  100  gm.  of  moist  soil  1  gm.  of  moist  soil  for  every 
per  centum  of  moisture  in  it.  King's  (45)  method  was  followed  throughout.  Five  hundred 
CO.  of  distilled  water  was  used  with  100  gm.  of  water-free  soil.  The  soil  was  placed  in  a  mortar, 
sufficient  water  added  to  make  a  thin  paste,  rubbed  with  a  pestle  for  3  minutes,  and  the 
mixture  transferred  to  a  porcelain  pitcher,  stirred  a  moment,  and  allowed  to  stand  20  minutes. 
Soil  and  water  were  then  transferred  to  a  Pasteur-Chamberland  filter  and  a  pressure  of  15  to 
20  pounds  applied. 

In  the  case  of  moist  soil  containing,  for  example,  20  per  cent  water,  480  cc.  of  water  was 
added,  making  a  total  of  500  cc.  precisely  the  same  as  in  case  of  the  dry  soil.  In  this  way, 
the  calculation  is  simplified  and  the  comparison  is  more  accurate  than  where  100  gm.  of  both 
moist  and  water-free  soil  are  used  and  500  cc.  of  water  added  to  each.  For  example,  if  100 
gm.  soil  contains  20  per  cent  water,  only  80  gm.  of  soil  are  washed,  500  cc.  -f-  20  gm.,  or  cc, 
of  water  from  the  soil,  a  total  of  520  cc.  The  ratio  of  soil  to  water  is  1 : 6.5,  instead  of  1 : 5,  as 
with  100  gm.  of  dry  soil  to  500  cc.  of  water,  for  which  our  plan  calls. 

The  first  50  cc.  of  the  soil  extract  was  discarded.  Two  125-cc.  portions  from  each  of  the 
duplicate  soil  samples,  or  four  portions  from  each  soil,  were  placed  in  silica  dishes  and 
reduced  to  dryness  on  a  water-bath,  dried  in  the  electric  oven  at  105''C.,  cooled  in  a 
desiccator,  and  weighed  on  an  analytical  balance.  This  weight  of  solids  represents  one- 
fourth  of  what  was  actually  dissolved  in  the  extract  from  the  original  100  gm.  of  soil. 


186  A.   F.    GUSTAFSON 

For  determining  nitrates,  two  50-cc.  samples  from  each  soil  duplicate,  four  in  all  from  each 
soil,  were  evaporated  to  dryness,  after  adding  a  few  drops  of  a  saturated  solution  of  sodiixm 
carbonate,  and  nitrates  determined  colorimetrically  according  to  Schreiner  and  Failyer  (89). 

Experiment  1 

The  object  of  this  experiment  is  to  study  the  effect  of  oven-drying  on  the 
soluble  solids  and  nitrate  content  of  four  types  of  soil  found  in  this  locality 
and  which  cover  a  wide  range  of  physical  composition. 

Samples  of  four  soils  were  collected  October  24,  1918,  from  the  Station 
farm  at  Ithaca, 

1.  Dunkirk  silt  loam 

A.  Surface,  yellow,  heavy  silt  to  clay  loam 

B.  Subsurface,  yellow  silt  loam 

Both  surface  and  subsurface  soil  contained  a  few  small  pebbles  and  were  very  low  in  organic 
matter.  This  soil  had  been  growing  a  heavy  sod  of  Kentucky  bluegrass  for  the  past  ten 
3reais. 

2.  Genesee  gravelly  loam 

A.  Surface,  brown  gravelly  loam,  much  coarse  material 

B.  Subsurface,  yellowish  brown  gravelly  loam  to  gravel 

This  was  a  very  coarse  gravelly  loam  containing  only  a  small  percentage  of  sand,  little  more 
than  a  trace  of  silt  and  clay,  and  was  low  in  organic  matter.     It  had  been  growing  alfalfa  and 
some  Kentucky  bluegrass  for  several  years. 
3  Dunkirk  fine  sandy  loam 

A.  Surface,  yellow  line,  sandy  loam 

B.  Subsurface,  yellow  sandy  loam,  sand  below  18  inches 

The  first  18  inches  of  this  soil  were  very  uniform  in  texture.     The  land  was  naturally  not  well 
supplied  with  organic  matter,  but  had  been  manured  somewhat  in  recent  years.     It  had 
been  fallowed  during  1918  and  was  being  planted  to  young  orchard. 
4.  Volusia  stony  loam 

A.  Surface,  brown  stony  loam,  loamy  phase,  not  many  stones  in  sample 

B.  Subsurface,  yellowish  bro^\'n  stony  loam,  more  fragments  of  stone  than  in  surface. 
This  sample  was  taken  near  the  boundary  between  this  type  and  Volusia  silt  loam  as  mapped 
by  Bonsteel,  Fippin  and  others  (4).    This  soil  has  been  growing  mixed  grasses  for  some  time. 

Table  1  gives  the  results  of  the  determinations  of  total  soluble  solids  and 
nitrates  in  heated  and  unheated  soils.  The  figures  in  the  last  column  of  tables 
1,  2,  3  and  6  are  in  each  case  the  product  of  the  probable  error  of  the  difference 
and  3.81.  It  is  the  quantity  of  total  solids  in  milligrams  that  the  dry  soil 
must  exceed  the  moist  (or  air-dry)  in  order  that  the  variation  may  be  con- 
sidered significant,  that  is,  that  the  odds  be  30:1  in  favor  of  the  difference 
being  due  to  variation  in  the  conditions  of  the  experiment  and  not  to  error 
in  manipulation. 

From  table  1,  it  is  readily  seen  that  in  every  case  the  dry  soil  yielded  more 
total  soluble  solids  than  did  the  moist  soil.  The  amount  of  nitrates  varies 
considcra1)ly.  In  five  of  the  eight  tube  samples,  denitrification  had  reduced 
the  nitrates  to  zero,  of  the  remaining  eleven  comparisons,  the  moist  soil  was 
slightly  higher  in  nitrates  in  six,  while  the  dry  was  ahead  in  five  cases,  so  no 
conclusion  as  to  effect  on  nitrates  can  be  drawn  from  this  experiment.     It 


EFFECT   OF   DRYING   SOILS   ON   WATER-SOLUBLE   CONSTITUENTS  187 

should  be  stated  that  there  was  considerable  variation  in  the  period  between 
sampling  and  the  determination  (the  last  one  being  made  August  15,  1919) 
so  that  biological  action  may  account  in  part  for  the  wide  variations  and  the 
frequent  high  probable  error  of  the  difference.  Occasionally  the  ice  was 
allowed  to  get  low  in  the  refrigerator  so  the  temperature  became  high  enough 
for  good  bacterial  growth.  There  is,  however,  no  case  in  which,  if  the  nitrates 
are  calculated  as  Ca(N03)2  and  deducted  from  the  total  solids,  that  the 
conclusion  or  its  significance  is  altered. 

Experiment  2 

The  purpose  of  this  experiment  was  to  study  the  effect  of  storage  for  nine 
weeks  at  8  to  12°C.  on  the  quantity  of  soluble  material  when  the  soils  were 
kept  under  somewhat  carefully  controlled  conditions  of  moisture  content,  but 
under  different  conditions  of  aeration.  Determinations  of  total  soluble  solids 
were  made  on  both  moist  and  dry  soils. 

On  October  23,  1919,  three  soils,  Dunkirk  silt  loam  (sod),  Dunkirk  silt 
loam  (stony),  and  Dunkirk  sandy  loam,  were  collected  and  treated  as  noted 
above.  The  first  and  third  are  the  same  soils  as  were  used  in  experiment  1 
and  are  similar  to  them  in  every  way,  these  samples  being  taken  within  a  few 
feet  of  the  others.  The  third  soil,  Dunkirk  silt  loam  (stony),  was  taken  from 
a  field  growing  rye  and  vetch.  It  had  been  well  manured  before  seeding  and 
has  received  considerable  fertilizer  during  the  past  few  years. 

Procedure 

The  tube  samples  were  sealed  with  paraffin  at  once  and  kept  in  the  refrigerator  for  a  period 
of  68  days  to  determine  the  effect  of  this  method  of  storage.  The  jars  containing 
the  auger  samples  were  kept  in  the  refrigerator  also.  Total  soluble  solids  and  nitrates  were 
determined  on  all  of  the  auger  samples  within  the  next  5  days,  beginning  on  October  24. 

The  remainder  of  each  of  these  samples  was  kept  in  the  ice-box  in  an  open  jar  to  allow  free 
aeration,  weighed  at  intervals  of  1  week,  and  distilled  water  added  to  make  up  for  any  loss 
by  evaporation  in  order  to  detemine  the  effect  of  this  method  of  storage  for  65  days.  The 
principal  difference  in  the  two  methods  of  storage  is  in  the  opportunity  for  aeration  in  the 
auger  sample  in  open  jars,  particularly  since  the  water  evaporating  was  compensated  at  inter- 
vals of  one  week. 

The  results  of  the  determinations  are  stated  in  table  2. 

These  figures  show  that  the  oven-dried  soil  compared  with  the  original  moist 
soil  had  in  the  two  silt  loams  three  to  five  times  as  much  soluble  solids  and  in 
the  sandy  loam  twice  as  much. 

The  Dunkirk  silt  loam  (sod)  contained  very  little  soluble  matter,  either 
mineral  or  organic,  and  but  little  more  than  a  trace  of  nitrates,  1.7  parts  per 
million  in  the  fresh  moist  sample.  This  is  in  close  accord  with  determinations 
made  on  this  soil  collected  the  previous  season,  though  both  nitrates  and  total 
solids  were  somewhat  higher  then. 


188 


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192  A.   F.   GUSTAFSON 

Close  scrutiny  of  this  table  reveals  that  in  three  cases  the  stored  auger  sample 
is  higher  in  total  soluble  solids  and  in  three  cases,  lower  than  the  fresh  sample. 
Determinations  made  on  fresh  auger  samples  and  on  the  stored  sealed-tube 
samples,  therefore,  are  comparable. 

In  each  soil  there  is  evidence  of  nitrification  in  the  open-jar-auger  sample, 
the  increases  in  the  three  soils  being  in  order  from  1.7  to  15.4  parts  per  million 
from  73  to  103  and  from  106  to  116.  In  some  cases  the  nitrates  run  higher  in 
the  sealed-tube  soil  and  in  some  lower  than  in  the  fresh  soil,  so  from  these 
meagre  data  no  conclusion  can  be  drawn  as  to  the  effect  on  nitrates  of  storing 
in  sealed  tubes  for  a  period  of  68  days. 

It  appears  that  the  effect  of  storing  at  a  temperature  of  8  to  12°C.  in  open 
jars  for  68  days  with  the  restoration  of  moisture  evaporated  at  intervals  of  a 
week  or  in  sealed  tubes  for  65  days  does  not  materially  affect  the  quantity  of 
total  soluble  solids  as  determined  by  1 : 5  extraction  with  distilled  water,  all 
of  the  soils  being  in  the  moist  state.  Storing  decreased  the  soluble  solids  as 
determined  in  the  water-free  condition  in  five  of  the  six  comparisons  made, 
the  losses,  however,  were  not  great. 

Experiment  3 

The  object  of  this  experiment  was  to  study  the  effect  on  soluble  solids  and 
nitrates  of  sun-,  air-  and  oven-drying  on  soils  that  had  been  water-logged  for 
a  considerable  period,  if,  indeed,  ever  dry  since  their  formation. 

In  July,  1919,  samples  of  a  drab  silt  loam  were  collected  near  Cayuga  Lake 
close  to  the  west  wall  of  the  valley  at  the  mouth  of  a  small  tributary.  The 
surface  and  subsurface  were  taken  with  a  steel  tube,  described  above.  The 
subsoil,  20  to  40  inches,  was  taken  with  an  auger  in  the  bottom  of  holes  left 
by  the  tube  after  taking  subsurface  stratum.  The  soil  suffered  little,  if  any, 
change  due  to  aeration  and  since  it  was  very  wet,  containing  73  to  108  per  cent 
of  moisture,  and  the  glass  containers  were  sealed  as  soon  as  possible  and  placed 
in  the  ice-box  on  reaching  the  laboratory. 

Determinations  were  made  the  same  as  in  experiment  1  during  the  next  few 
days  on  the  wet  and  corresponding  oven-dry  samples  and  in  the  same  way  on 
the  sun-dried  samples  on  August  8. 

Another  set  of  samples  was  collected  on  October  16,  1919,  south  of  Ithaca, 
near  the  east  wall  of  the  valley  at  the  mouth  of  a  small  stream.  This  soil, 
also  a  drab  silt  loam,  was  not  so  wet  as  the  other  and  contained  nitrates  in 
the  subsurface,  whereas  the  other  soil  had  none  in  the  subsurface. 

In  every  case  the  wet  soil  was  mixed  thoroughly  by  hand  and  the  total 
moisture  determined  in  triplicate  instead  of  in  duplicate,  as  with  all  other  soils. 

The  "wet"  samples  were  oven-dried  during  the  night  and  determinations 
made  the  following  day,  October  17.  Half  of  the  soil  was  set  out  to  dry  in  the 
laboratory,  as  there  is  usually  not  much  sunshine  and  rainfall  is  frequent  here  at 
this  season.    Determinations  were  made  as  soon  as  the  soil  was  entirely  air-dry. 

The  results  are  given  in  table  3. 


EFFECT  OF  DR\T[NG    SOILS   ON  WATER-SOLUBLE   CONSTITUENTS  193 


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194 


A.   F.    GUSTAFSON 


It  will  be  noted  that  oven-drying  materially  increased  the  total  soluble 
sohds  in  all  of  the  wet  samples,  air-drying  brought  about  a  marked  increase 
and  oven-drying  the  air-dry  soil  still  further  increased  the  total  soluble  solids, 
as  shown  in  table  4. 

In  the  first  two  columns  of  percentages,  the  increase  is  based  on  the  total 
soluble  solids  in  wet  soil  but  in  the  third,  the  percentage  increase  is  based  on 
the  total  soluble  solids  in  the  air-dry  soil.  This  increase  calculated  on  the 
same  basis  as  the  first  two  is,  for  the  respective  samples,  83,  177,  290,  223  and 
534  per  cent.  The  increase  due  to  air-drying  before  oven-drying  cannot  be 
due  to  any  nitrification  during  the  slow  drying  at  ordinary  temperature,  as 
the  increase  in  nitrates  was  exceedingly  slight,  wholly  insufficient,  calculated 
as  Ca(N03)2  to  account  for  the  change. 

The  marked  effect  of  air-drying  on  these  swamp  soils  may  help  to  account 
for  the  relatively  high  productivity  of  such  soils  after  a  few  seasons  of  cul- 
tivation, as  against  their  low  productivity  when  newly  turned  by  the  plow. 

TABLE  4 
Increase  in  total  soluble  sails  due  to  drying 


SOIL 

STRATUM 

INCREASE 

DUE  TO 
OVEN-DRY- 
ING WET 
SOIL 

INCREASE 

DUE  TO 

AIR-DRYING 

WET  SOIL 

INCREASE 

DUE  TO 
OVEN-DRY- 
ING   AIR-DRY 

son. 

per  cent 

per  cent 

per  ctnt 

Surface,  0  to  8  inches 

60 

23 

50 

Drab  silt  loam  near  lake   <. 

Subsurface,  12  to  20  inches 

62 

74 

59 

Subsoil,  20  to  40  inches 

200 

94 

104 

Drab  silt  loam  south  of     f 

Surface,  0  to  8  inches 

167 

50 

116 

Ithaca                             \ 

Subsoil,  12  to  20  inches 

412 

150 

154 

Kelley  and  McGeorge  (40)  state: 

The  solubih'ty  of  soUs  used  in  aquatic  agriculture  is  abnormally  high,  but  upon  drying 
out  these  become  much  less  soluble  and  approach  a  state  similar  to  that  existing  in  aerated 
soils.  When  such  soUs  are  heated  after  drying,  they  seem  to  undergo  changes  of  the  same 
order  as  are  produced  in  dry-land  (ordinary  cultivated)  soils. 

The  work  here  reported,  either  experiment  3  or  4,  is  not  in  accord  with  their 
conclusions,  as  these  soils  when  air-dried,  had,  in  every  case,  more  soluble 
salts  than  the  same  soils  when  wet. 


Experiment  4 

The  object  of  this  experiment  was  to  study  the  effects  of  oven-drying  on  a 
wide  range  of  fine-grained  soils  containing  varied  amounts  of  organic  matter 
at  three  moisture-contents,  viz.,  air-dry,  optimum,  and  water-logged,  with 
the  soil  kept  in  the  latter  two  conditions  for  a  period  of  9  weeks. 

Six  soils  were  used,  ranging  in  texture  from  clay  to  sandy  loam: 


EFFECT  OF  DRYING   SOILS   ON  WATER-SOLUBLE  CONSTITUENTS 


195 


1.  Drab,'  or  (Sharkey,*)  clay.  This  is  a  drab  colored  clay  soil,  not  well  supplied  with  organic 
matter,  stifiF  and  more  or  less  impervious  to  water,  very  diflkult  to  work  as  it  is  exceedingly 
tenacious  when  wet  and  cloddy  when  dr>'.  It  occurs  in  large  areas  in  the  poorly  drained 
portions  of  the  Mississippi  bottom  lands,  especially  south  of  St.  Louis.  It  is  more  fully 
described  by  Hopkins,  Mosier  and  associates  (34),  Marbut  and  associates  (65),  and  as  Yazoo 
clay  by  Coffey  and  others  (11). 

2.  Black  clay  loatn^  (Marshall  black  clay  loam).  This  is  a  black  clay  loam  soil,  well  sup- 
plied with  organic  matter.  It  occurs  in  flat,  depressed  areas,  former  ponds  or  lakes,  and  is 
very  productive  when  thoroughly  drained.  It  is  described  more  fully  by  Hopkins,  Mosier, 
et  al.  {2)3),  Marbut  (65)  and  as  Miami  black  clay  loam  by  Coffey,  Mosier  et  al.  (12). 

3.  Brown  silt  loam  (Marshall  silt  loam).  This  is  a  brown  silt  loam  soil  of  good  open  texture, 
well  supplied  with  organic  matter,  and  very  productive,  occupying  the  rolling  prairies  of 
Illinois,  Indiana  and  Iowa.  Described  by  Hopkins,  Mosier  et  al.  (35),  Marbut  (65)  and 
Coffey  et  al.   (13). 

TABLE  5 

Organic  matter*  contained  in  these  soils 


1.  Drab  clay 

2.  Black  clay  loam 

3.  Brown  silt  loam 

4.  YeUow-gray  silt  loam 

5.  White  silt  loam 

6.  Dunkirk  fine  sandy  loam 


ORGANIC 
CARBON 


per  cent 

2.07 
3.19 

2.78 
1.67 

0.435 
1.856t 


TOTAL 
ORGANIC 
MATTER 


per  cent 

3.57 
5.5 

4.8 
2.9 

0.75 
3.20 


MOISTURE 
EQUrVALENT 


per  cent 
41.6 
32.4 

28.0 
20.7 


*  Figures  on  soils  1  to  4  furnished  by  Professor  J.  G.  Mosier. 
t  This  determination  was  kindly  made  by  Dr.  F.  A.  Carlson. 

4.  Yellow-gray  silt  loam  (Knox  silt  loam).  This  is  a  light  colored,  rolling  timber  soil,  not 
well  supplied  with  organic  matter.  More  fully  described  by  Hopkins,  Mosier  et  al.  (33), 
Marbut  (65)  and  as  Miami  silt  loam  by  Coffey,  Mosier  and  others  (13). 

5.  White  silt  loam.  This  soil  was  not  recognized  as  a  separate  type  by  the  Bureau  of  Soils, 
as  its  work  in  Illinois  was  done  during  the  beginning  of  American  soil  surveying.  It  is  a 
very  light  gray  silt  loam,  underlaid  by  a  decidedly  impervious  stratum,  known  as  "tight 
clay."  It  is  an  unproductive  virgin  timber  soil,  very  low  in  organic  matter,  in  fact  ahnost 
nitrogen  free,  having  but  0.7  per  cent  of  organic  matter.  This  soil  is  more  fully  described 
by  Hopkins,  Mosier  et  al.  (32). 

6.  Sandy  loam.    This  is  the  same  soil  that  was  used  in  e.xperiments  1  and  2. 

Soils  1  to  5,  inclusive,  are  surface  soils,  7  to  8  inches  deep.  Soils  1  to  4  have 
been  stored  in  the  air-dry  state  for  two  or  more  years  in  an  attic  where  the 
humidity  is  very  low  and  the  temperature  at  times  in  summer,  rather  high. 

Table  5  gives  the  content  of  organic  matter  in  these  soils. 

»  Name  used  by  Illinois  Agricultural  Experiment  Station. 
*  Name  used  by  United  States  Bureau  of  Soils,  in  Bui.  96,  p.  738. 

5  Soils  1  to  5,  inclusive,  were  collected  by  the  writer  while  a  member  of  the  staff  of  the 
Agronomy  Department,  College  of  Agriculture,  University  of  Illinois. 


196  A.   F.    GUSTAFSON 

Organic  carbon  was  determined  by  the  Parr  bomb-calorimeter  method, 
CO2  was  measured  and  reduced  to  standard  P  and  T  from  which  C  was  cal- 
culated. C  X  1.724  (Wolff  factor)  gives  organic  matter.  This  is  not  claimed 
to  be  absolutely  accurate  nor  strictly  comparable  since  the  carbon  content 
of  soil  organic  matter  varies  with  its  age  and  the  conditions  under  which  de- 
composition has  occurred.  The  organic  matter  in  white  silt  loam,  for  example, 
is  probably  more  highly  carbonized  than  that  in  brown  silt  loam  and  that  in 
drab  clay,  a  swamp  soil,  has  been  affected  by  a  different  type  of  decom- 
position from  bro^\^l  silt  loam,  a  well-drained  type.  However,  the  figure  for 
organic  matter  is  of  value  in  a  comparative  way  when,  as  in  these  soils,  the 
differences  between  them  are  marked. 

Procedure 

The  soils  were  air-dried,  worked  over  with  a  rolling  pin,  passed  through  a  2-nun.  screen, 
thoroughly  mixed  and  divided  into  three  portions,  a,  b,  and  c.  On  samples  of  a  the  usual  de- 
terminations of  total  soluble  solids  and  nitrates  were  made  in  the  original  air-dry  and  in  the 
water-free  condition.  To  b  distilled  water  was  added,  and  worked  by  hand,  until  it  reached 
what  might  be  termed  "optimum"  moisture  content  when  the  soil  was  placed  in  2-liter  ear- 
thenware jars.  These  were  weighed  on  a  solution  scale  the  next  day  and  at  the  end  of  each 
succeedmg  7-day  period,  when  distilled  water  was  added  to  restore  that  lost  by  evaporation. 
To  c,  in  similar  jars,  distilled  water  was  added  to  a  point  of  saturation  and  more  water 
was  poured  on  as  needed  to  keep  the  soil  submerged.  Then  b  and  c  were  kept  in  the  labor- 
atory for  nine  weeks,  except  the  Dunkirk  sandy  loam  which  was  kept  only  8  weeks.  The 
regular  determinations  were  made  on  both  moist  and  water-free  samples  at  the  end  of  this 
time. 

Results  are  given  in  table  6. 

Table  6  has  several  outstanding  features.  The  increase  in  total  solids  ex- 
tracted from  soils  1,  2  and  3,  well  supplied  with  organic  matter,  when  the 
original  air-dry  soil  is  dried  in  the  oven  at  105°C.  is  very  marked;  in  soils  4,  5 
and  6,  low  in  organic  matter,  the  actual  increase  due  to  drying  is  less,  but  the 
amount  of  soluble  solids  varies  from  nearly  twice  to  almost  three  times  as 
much  as  that  in  the  air-dry  soil.  In  all,  except  white  silt  loam,  which  is  very 
low  in  organic  matter,  the  moist  b  samples  kept  9  weeks  at  optimum  moisture- 
content  had  a  higher  quantity  of  soluble  material  than  did  the  air-dry  soil, 
and  the  dry  b  soil  exceeded  that  water-freed  directly  from  the  original  air-dry 
condition.  This  increase  may  be  accounted  for  by  the  increase  in  nitrates, 
calculated  as  Ca(N03)2- 

The  saturated  c  samples  in  the  wet  condition  showed  more  total  soluble 
salts  than  either  of  the  others,  even  though  the  nitrates  had  disappeared. 
When  oven-dried,  this  soil  showed  the  highest  soluble  salt  content  in  five  of 
the  six  soils,  and  the  sixth  was  but  0.8  mgm.  below  the  next  higher  soil,  the 
water-freed,  moist  Dunkirk  sandy  loam.  This  may  be  accounted  for  in  part 
by  the  very  large  amount  of  water  in  these  soils  shown  in  table  6  to  be  75.7 
per  cent  in  drab  clay  down  to  37.8  per  cent  in  Dunkirk  sandy  loam.  Here 
the  soil  solution  is  much  more  dilute  and  more  solids  tend  to  dissolve,  as  the 


EFFECT   OF   DRYING   SOILS   ON   WATER-SOLUBLE  CONSTITUENTS  197 

solution  is  probably  far  from  saturated  with  respect  to  any  of  the  salts.  This 
soil  solution  upon  adding  distilled  water  to  make  up  the  total  500  cc.  becomes 
a  part  of  the  500  cc.  and  the  final  result  is  a  more  concentrated  solution  as 
shown  by  table  6.  When  the  saturated  soil  was  placed  in  the  oven,  water 
stood  on  its  surface,  so  the  oven-drying  process  required  more  than  the  usual 
8  hours.  This,  it  has  been  suggested,  brings  more  organic  matter  and  much 
iron  and  alumina  into  solution. 

Experiment  5.  Determination  of  hygroscopic  coefficient 

In  the  hope  of  securing  information  which  might  shed  a  bit  of  light  on  the 
cause  of  the  increase  in  soluble  material  in  soils  due  to  heating,  two  small 
pieces  of  experimental  work  were  undertaken,  viz.  (experiment  5),  the  deter- 
mination of  the  hygroscopic  capacity,  or  coefficient,  of  the  soils  used  in  experi- 
ment 4  and  (experiment  6)  a  study  of  the  retention  of  potassium  nitrate  by 
different  grades  of  sand. 

The  soils  are  those  used  in  experiment  4  which  range  from  clay  to  sandy 
loam. 

Procedure 

In  order  to  have  the  soils  as  uniform  as  possible,  they  were  passed  through  a  1-mm.  sieve. 
Duplicate  samples  of  air-dry  soil  equivalent  to  approximately  2  gm.  of  water-free  soil  were 
weighed  directly  into  weighing  bottles,  7  cm.  in  diameter.  The  soil  was  spread  out  in  a  uni- 
formly thin  layer  over  the  bottom  and  exposed  to  a  saturated  atmosphere  in  a  humidifier.* 
Strips  of  filter  paper  were  used  as  wicks,  increasing  the  surface  of  contact  between  air  and 
water  in  order  to  insure  complete  saturation  of  the  air.  By  means  of  a  water-pump  the  air 
pressure  within  the  humidifiers  was  reduced  by  several  centimeters  in  order  to  hasten  satura- 
tion and  reduce  condensation.  To  avoid  marked  sudden  changes  in  temperature,  the  humidi- 
fiers were  placed  in  a  thick-walled  wooden  box  lined  with  asbestos.  This  was  first  located 
in  a  cold  room  and  heated  electrically,  a  thermostat  being  used  for  maintaining  a  constant 
temperature.  It  was  found  after  6  weeks'  work,  however,  that  the  external  temperature 
of  winter  varied  so  much  that  the  thermostat  and  heating  apparatus  were  incapable  of  main- 
taining a  sufliciently  constant  temperature.  In  several  instances  there  was  a  sudden  drop  in 
outdoor  temperature  the  day  before  weighings  were  to  be  made.  This  brought  about  con- 
densation in  the  soil,  giving  hygroscopic  coefficients  too  high  and  far  from  uniform. 

The  next  step  was  to  place  the  entire  apparatus  in  a  deep,  unheated  basement  room. 
Here  the  temperature  to  which  the  soils  were  subjected  remained  fairly  constant.  The 
maximum  variation  in  room  temperature  during  the  first  week  was  from  61  to  64°F.,  and 
inside  of  the  box  from  15.5  to  l^C;  the  second  week  the  corresponding  temperatures  were 
60.5  to  65.5°F.  for  the  room  and  from  15  to  18°C.  inside  the  box.  There  did  not  appear  to 
be  any  condensation  and  yet  there  is  not  an  altogether  satisfactory  agreement  of  duplicate 
determinations  made  the  first  week  on  soils  4,  5  and  6. 

The  soils  were  kept  in  the  saturated  atmosphere  for  a  period  of  7  days  when  the  humidifiers 
were  removed  from  the  constant-temperature  box.  Before  removing  the  lid  of  humidifiers, 
the  pressure  was  equalized  by  admitting  air  very  slowly  through  the  side  tube.  Upon  remov- 
ing the  weighing  bottles  from  the  humidifier,  the  lids  were  immediately  and  tightly  inserted 

^  The  humidifier  was  a  large  desiccator  whose  dehydrating  substance  had  been  replaced 
by  a  10  per  cent  solution  of  sulfuric  acid  to  furnish  the  water  vapor.  The  desiccators  are 
supplied  with  side  tube  and  stop  cock. 


198 


A.   F.    GUSTATSON 


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EFFECT  OF  DRYING   SOILS   ON  WATER-SOLUBLE   CONSTITUENTS  199 


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200 


A.   F.    GUSTAFSON 


to  prevent  evaporation  and  the  bottles  with  soil  weighed  at  once  after  wiping  them  perfectly 
dry.  After  weighing,  the  soil  was  dried  in  the  bottles  at  105°C.  for  8  hours  and  again  weighed. 
The  loss  is  the  hygroscopic  moisture  or,  expressed  as  per  cent  on  the  basis  of  oven-dry  soil,  the 
hygroscopic  coefficient. 

The  results  of  the  determinations  appear  in  table  7. 

As  pointed  out  by  Beaumont  (3,  page  492^93),  the  probable  error  of  deter- 
minations of  hygroscopic  coefficient  is  high.  The  accuracy  of  this  statement 
is  well  borne  out  by  the  figures  in  table  7,  His  results  indicated  that  slight 
variations  in  temperature  made  little  difference  in  adsorption  of  vi^ater  vapor 
so  the  only  effort  in  this  work  was  to  keep  the  temperature  sufiiciently  con- 
stant to  prevent  condensation  of  free  water  on  the  particles,  or  in  the  inter- 

TABLE  7 
Hygroscopic  coefficients  of  air-dry  soils  used  in  experiment  4 


water  absorbed  in  7  days 

mean 

o 
a 

u 

i 

5^ 

< 

< 
o 
OS 
o 

TOTAL  SOLUBLE  SALTS 
AT    OPTIMUM  MOIS- 
TURE* 

2  Sag  2 

ri  w  H     w 

son. 

First  trial 

Second  trial 

AVERAGE    SC 
SALT    CONl 
AIR-DRY.  01 
MOISTURE, 
WATER-FRI 

A 

B 

A 

B 

per 

cent  of 
dry  soil 

per 
cent 

mgm. 

mgm. 

1 .  Drab  clay . .  . 

11.66 

11.62 

11.30 

11.62 

11.550±0.061 

5.59 

3.57 

81.8 

115.4 

2.  Black      clay 

loam 

9.95 

10.24 

9.94 

10.02 

10.037±0.493 

5.15 

5.50 

76.2 

125.0 

.1.  Brown      silt 

loam 

4.45 

4.62 

4.41 

4.47 

4.487±0.0322 

2.33 

4.80 

97.5 

140.1 

4.  Yellow   gray 

silt  loam  .  . 

2.05 

2.50 

2.30 

2.26 

2.277±0.0598 

1.24 

2.90 

70.8 

83.8 

5.  White       silt 

loam 

1.55 

1.95 

1.85 

1.83 

1.795  ±0.0299 

1.25 

0.75 

26.0 

62.2 

6.  Dunkirk  fine 

sandy  loam 

1.95 

2.44 

2.22 

2.48 

2.272±0.0915 

0.90 

3.20 

77.4 

99.5 

*  Data  taken  from  table  6. 

stices  of  the  soil.  This  latter  seems  to  have  occurred  during  the  early  part  of 
this  work  as  the  hygroscopic  coefficient  was  high  and  quite  erratic.  These 
figures  seem  to  bear  out  Beaumont's  conclusion,  also,  that  other  factors  than 
total  surface  aflfect  the  adsorption  of  water.  Soils  4  and  5  are  very  similar 
in  texture,  consequently  in  total  surface,  and  the  hygroscopic  moisture  actually 
in  the  soils,  air-dry,  is  the  same,  yet  when  exposed  to  the  same  saturated 
atmosphere,  soil  4,  with  higher  organic-matter  and  soluble-salt  content,  ad- 
sorbs 0.482  per  cent  more  actual  moisture,  27  per  cent  excess  over  soil  5,  the 
one  of  lower  salt-  and  organic-content.  In  this  connection,  let  us  compare 
soils  5  and  6,  in  table  7.  White  silt  loam  has  much  more  surface  than  Dunkirk 
fine  sandy  loam.''    In  the  air-dry  state  they  appear  in  their  right  order  as 

^  No  mechanical  analysis  available. 


EFFECT   OF   DRYING    SOILS   ON   WATER-SOLUBLE  CONSTITUENTS  201 

regards  hygroscopic  moisture  and  surface  having,  respectively,  1.25  and  0.90 
per  cent  hygroscopic  moisture.  However,  when  exposed  to  a  saturated  atmos- 
phere for  7  days,  they  stand  in  a  different  relationship  to  each  other,  their 
positions  being  reversed,  and  instead  of  the  soil  with  greater  surface  absorbing 
more  moisture,  more  is  taken  up  by  the  soil  which  has  less  surface,  but  con- 
tains more  soluble  salts.  This  tends  to  show  that  within  certain  limits,  at 
least,  soluble  salts  are  of  sufficient  importance  to  reverse  the  normal  effect 
of  total  surface  exposed  by  a  soil. 

Considering  table  7  in  a  broad,  general  way,  the  hygroscopic  moisture  con- 
tent in  the  air-dry  soil  bears  a  normal  relationship  to  the  total  surface,  and 
when  we  consider  surface  and  organic-matter  content  this  same  general  re- 
lationship holds  for  hygroscopic  coefficient  except  in  case  of  the  sandy  loam 
where  the  discrepancy  is  due  to  its  large  quantity  of  soluble  salts.  The  dif- 
ficulty here  lies  in  that  we  have  not  a  single  variable  factor,  but  several,  viz., 
size  of  particles,  total  surface,  organic  matter,  and  soluble  salts. 

Since  it  is  almost,  if  not  wholly  impossible  to  control  all  factors  at  once, 
it  may  be  necessary  to  work  with  synthetic  soils,  varjdng  but  a  single  factor 
at  a  time.  These  determinations  of  hygroscopic  coefficients  cannot  yield  much 
valuable  evidence,  except  that,  in  a  general  way,  the  soils  with  the  highest 
percentage  of  clay  and  colloids  have  the  highest  hygroscopic  coefficients  and 
within  the  limits  of  this  experiment  have  the  highest  soluble  salt  content. 
However,  the  data  are  so  meagre  that  no  definite  safe  conclusion  may  be  drawn. 

Experiment  6.  Retention  of  nitrate  by  quartz  and  white  silt  loam 

The  purpose  of  this  experiment  was  to  study  the  question  whether  clean 
quartz  sand  holds  potassium  nitrate,  and  if  so,  to  what  extent.  This  salt 
was  selected  because  the  acid  radical  is  not  generally  supposed  to  be  adsorbed 
to  an  appreciable  degree,  and  also  because  it  was  available  as  a  chemically 
pure  substance. 

The  material  used  was  a  clean  ground  quartz.  It  was  first  leached  with  a 
10  per  cent  solution  of  hydrochloric  acid  to  remove  any  possible  soluble  ma- 
terial, then  washed  free  of  the  acid  and  air-dried.  It  was  then  sifted  into  four 
grades,  as  used  by  the  United  States  Bureau  of  Soils: 

Diameter 
mm. 

Coarse  sand 1 .00-0.50 

Medium  sand 0.50-0.25 

Fine  sand 0.25-0.10 

Very  fine  sand 0. 10-0.05 

White  silt  loam  from  experiments  4  and  5  was  used  also,  since  in  the  air-dry 
condition  it  was  essentially  devoid  of  nitrates. 

The  water-holding  capacity  of  50  gm.  of  each  of  these  materials  was  then 
determined  experimentally.  Water  was  added  from  a  burette  and  the  ma- 
terials were  found  to  hold,  without  any  loss  by  percolation  on  standing,  the 


202  A.   F.    GUSTAFSON 

following  quantities:  coarse  sand,   10  cc;  medium  sand,  10  cc;  fine  sand, 
15  cc;  very  fine  sand,  17  cc;  white  silt  loam,  18  cc 

According  to  Mosier  and  Gustafson  (68)  the  surface  per  gram  of  the  different 
grades,  assuming  perfect  spheres  of  average  diameter  for  the  grades,  is  as 
follows:  coarse  sand,  30.2  sq.  cm.;  medium  sand,  60.4  sq.  cm.;  fine  sand, 
129.3  sq.  cm.;  very  fine  sand,  302.1  sq.  cm.;  white  silt  loam,  2270.7  sq.  cm. 
Analysis^  of  this  latter  soil  shows  (Bureau  of  Soils  sizes)  1.5  per  cent  medium 
sand  and  coarser  grades,  1.7  per  cent  fine  sand,  7.5  per  cent  very  fine  sand, 
70.6  per  cent  silt,  and  18.3  per  cent  clay.  The  calculation  of  the  surface  per 
gram  of  white  silt  loam  was  based  upon  these  percentages,  the  surface  areas 
given  above,  and  the  assumption  that  824.8  sq.  cm.  is  the  surface  of  1  gm. 
of  silt  and  that  9090.2  sq.  cm.  is  the  surface  of  1  gm.  of  clay. 

The  figures  for  total  surface  per  gram  are  undoubtedly  more  nearly  accurate 
for  white  silt  loam  than  for  the  quartz  since  the  latter  is  angular  and  of  all 
conceivable  shapes  with  no  spheres.  The  surface  of  the  quartz  must  be 
considerably  greater  than  the  figures  shQw,  whereas  in  the  white  silt  loam  soil 
the  angles  have  been  worn  off  the  particles  to  some  extent,  bringing  them 
somewhat  toward  the  spherical  shape — yet  the  figures  at  best  are  but  an 
approximation  which  may  be  of  some  value  for  purposes  of  discussion. 

Solutions  of  potassium  nitrate  were  then  made  up  of  such  strength  that 
1  cc  of  the  first  solution  contained  0.1  mgm.  of  nitrate  and  the  other,  0.5 
mgm.  of  nitrate.  The  hygroscopic  capacity  of  quartz  is  so  low  that  this  factor 
was  ignored.  A  quantity  of  potassium  nitrate  solution  equal  to  the  water- 
holding  capacity  was  added  from  an  accurate  burette  to  each  of  four  50-gm. 
samples  of  the  grades  of  quartz  and  of  white  silt  loam.  These  moistened 
samples  were  covered  to  prevent  evaporation  and  set  aside  over  night  to  per- 
mit of  any  reaction  or  adjustment  in  the  moist  mass,  after  which  two  samples 
of  each  were  placed  in  the  oven  at  105°C.  for  8  hours.  Nitrates  were  deter- 
mined immediately  on  the  other  two  samples.  Each  was  placed  in  a  500-cc. 
beaker  and  distilled  water  added  to  make  a  total  of  250  cc;  for  example,  to 
the  coarse  sand  containing  10  cc.  of  KNO3  solution,  240  cc.  of  distilled  water 
was  added  and  to  the  very  fine  sand  having  17  cc.  of  the  solution,  233  cc.  of  water 
was  added.  Thus  the  relationship  throughout  was  1  part  of  soil  or  quartz 
to  5  of  water. 

This  experiment  was  run  in  two  parts,  6a  and  6b.  In  the  first  part,  the 
nitrate  solution  used  contained  100  parts  per  million,  or  0.1  mgm.  per  cubic 
centimeter  of  nitrate  and  in  the  second,  the  solution  contained  500  parts  per 
miUion  or  0.5  mgm.  per  cubic  centimeter.  In  all  other  respects  the  two  trials 
were  identical.  The  stronger  solution  was  used  in  the  second  trial  because  a 
dilution  of  10  cc.  of  the  first  solution  to  250  cc  was  considered  too  great  for 
securing  results  of  the  degree  of  accuracy  desired. 

The  results  of  the  first  set  of  determinations  are  given  in  table  8. 

The  results  of  the  second  set  of  determinations  are  given  in  table  9. 

*  This  analysis  was  kindly  furnished  by  Dr.  Bizzell  and  Dr.  Buckman. 


EFFECT  OF  DRYING   SOILS   ON   WATER-SOLUBLE  CONSTITUENTS 

TABLE  8 

Nitrate  recovered  from  ground  quartz  and  while  silt  loam 

{Nitrate  solution,  100  p.  p.  m.  or  0.1  mgm.  per  cc.) 


203 


SIZE   OF  MATERIAL 

CONDITION 

AMOUNT 

NITRATE 

ADDED 

FIRST 
EXTRACTION 

SECOND 
EXTRACTION 

THIRD 
EXTRACTION 

RECOV- 
ERCD  BY 

NOs 

found 

NOjin 

250  cc. 

NOi 

found 

NO,  in 

250  cc. 

NOa 

found 

NO,  in 
250  cc. 

EXTRAC- 
TION 

mgm. 

p.  p.m.* 

mgm.* 

p.  p.  m.* 

mgm. 

p.  p.  m.* 

mgm. 

per  cent 

r 

Coarse  sand..  . .{ 

Moist 
Dry 

1.0 
1.0 

3.22 

3.15 

0.805 
0.79 

0.48 
Trace 

0.12 
Trace 

0.33 
0.36 

0.08 
0.09 

80.50 
79.00 

Medium  sand..  .< 

Moist 
Dry 

1.0 
1.0 

3.17 
2.82 

0.79 
0.705 

0.56 
Trace 

0.14 
Trace 

0.32 
0.32 

0.08 
0.08 

79.00 
70.50 

Fine  sand < 

IMoist 
Dry 

1.5 
1.5 

4.67 
4.11 

1.17 
1.03 

1.03 
0.62 

0.26 
0.15 

0.42 
Trace 

0.10 
Trace 

78.00 
68.67 

Very  fine  sand..< 

Moist 
Dry 

1.7 
1.7 

4.59 
4.41 

1.15 
1.10 

0.96 
0.71 

0.24 
0.18 

Trace 
0.25 

Trace 
0.06 

67.64 
64.70 

White  silt  loam.. 

Moist 

1.8 

5.57t 

1.393 

77.40 

*  Average  of  four  determinations. 
t  Average  of  eight  determinations. 


TABLE  9 

Nitrate  recovered  from  ground  quartz 

{Nitrate  solution,  500  p.  p.  m.  or  0.5  mgm.  per  cc.) 


CONDITION 

AMOUNT 

OF 
NITRATE 
ADDED 

PmST  EXTRACTION 

SECOND  EXTRACTION 

TOTAL 

NO, 

NO, 

found 

NO,  in  250  cc.  if 
homogeneous 

NO, 
found 

NO,  in  250  cc.  if 
homogeneous 

RECOV- 
ERED 

Coarse  sand < 

Medium  sand..  .1 

Fine  sand I 

Very  fine  sand..\ 

Moist 
Dry 

Moist 
Dry 

Moist 
Dry 

Moist 
Dry 

mgm. 

5.0 
5.0 

7.5 
8.5 

p.  p.m.* 
17.74 

15.30 

15.45 
14.75 

28.51 

n.n 

30.78 
29.26 

mgm. 
4.435 

3.825 

3.886 
3.687 

7.127 
6.817 

7.695 
7.315 

per  cent 

88.7 
76.5 

77.5 
73.7 

95.0 
91.0 

90.6 
86.0 

p.  p.m.* 
1.21 
0.49 

1.103 
0.48 

1.56 
0.48 

2.06 
0.703 

mgm. 

0.302 
0.122 

0.276 
0.120 

0.390 
0.120 

0.515 
0.176 

per  cent 

6.0 

2.4 

5.5 
2.4 

5.2 
1.6 

6.0 
2.3 

per  unt 

94.7 
78.9 

83.0 
76.1 

100.2 
92.6 

96.6 
88.3 

*  Average  of  four  determinations. 


A  glance  at  tables  8  and  9  shows  that  the  recover  of  nitrate  was  less 
complete  with  the  more  dilute  solution,  the  average  percentage  of  recovery 
being  76.3  for  the  moist  quartz  and  70.7  for  the  oven-dry  quartz,  compared 


204 


A.   F.    GUSTAFSON 


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EFFECT   OF   DRYING   SOILS   ON  WATER-SOLUBLE  CONSTITUENTS 


205 


with  87.9  and  81.8  which  are  the  corresponding  figures  for  the  more  con- 
centrated solution.  Thus  it  is  seen  that  the  recovery  from  the  oven-dry 
quartz  was  less  in  both  cases,  less  by  5.6  per  cent  for  the  dilute  solution  and 
by  6.1  per  cent  for  the  more  concentrated  solution.  This  relationship  holds 
throughout  the  second  extraction  also.  This  seems  to  indicate  a  real  loss  of 
nitrate  due  to  heating  in  the  oven  for  8  hours  at  105°C. 

In  order  to  test  this  point  further,  eight  10-cc.  samples  of  a  nitrate  solution 
containing  100  parts  per  million  and  eight  5-cc.  portions  containing  500 
parts  per  milhon  were  treated  with  a  few  drops  of  saturated  sodium  carbonate 
solution  and  evaporated  to  dryness  on  the  water-bath.  The  nitrates  in  tour 
samples  of  each  were  determined  at  once  in  the  usual  manner.  The  remaining 
four  samples  of  each  concentration  were  dried  in  the  oven  at  about  105°C. 
for  8  and  21  hours,  respectively.  The  results  of  all  the  determinations  are 
given  in  table  11. 

TABLE  11 
Efect  of  heating  at  105°C.  on  quantity  of  nitra'e  recovered  from  quartz  sand 


CONCENTRATION 

GRADE  or  MATERIAL 

About  0,1  mgm  per 
cubic  centimeter 

About  O.S  mgm.  per 
cubic  centimeter 

Not  heated 

After 
heating 

Not  heated 

After 
heating 

Coarse  sand                  

40.125 
40.375 
40.750 
40.000 

43.75* 
45.20* 
45.40* 

36.00 

37.25 
37.00 

37.25 

41.00 

Medium  sand 

41.00 

Fine  sand 

40.25 

Very  fine  sand 

40.50 

Average 

40.31 

44.59 

36.87 

40.69 

Percentage  recovery 

100.00 

90.39 

100.00 

90.86 

*  Average  of  five  readings,  others  average  of  four  readings. 

Since  all  of  the  above  were  compared  with  the  same  standard  and  all  samples 
of  each  concentration  were  diluted  to  the  same  extent,  the  average  colorimeter 
readings  bear  to  each  other  exactly  the  same  relationship  as  would  the  actual 
milligrams  of  nitrate,  so  the  reading  of  unheated  samples  is  considered  100  and 
the  other  found  thus:  44.59  :  40.31  =  100  :  x.  Of  the  weaker  solution,  10  cc. 
was  diluted  to  1000  cc.  and  of  the  stronger,  5  cc,  to  2500  cc.  in  order  to  bring 
each  to  approximately  1  part  per  million  for  reading.  From  these  figures 
the  total  milligrams  of  nitrate  in  each  can  be  calculated.  These  figures  show 
a  loss  of  nearly  10  per  cent  of  the  nitrate  after  the  period  of  heating  at  slightly 
above  the  boiling  point.  This  is  in  accord  with  the  earlier  work  recorded  in 
this  paper.  For  this  reason  further  discussion  here  will  deal  with  the  unheated 
materials  only. 

In  the  case  of  the  coarse  and  medium  grades  with  the  same  quantity  of 
nitrate  added,  the  medium  holds  more,  or  gives  up  less,  nitrate  at  both 


SOIL  SCIENCE,   VOL.   XIII,   NO.   3 


206  A.   F.    GUSTAFSON 

concentrations;  the  same  relationship  holds  at  both  concentrations  when  we 
compare  the  nitrate  recovered  from  the  fine  and  very  fine  grades  receiving, 
respectively,  15  and  17  cc.  of  nitrate  solution.  This  tends  to  show  that  the 
difference  is  due  to  a  surface  effect. 

Let  us  consider  the  very  fine  sand  grade  in  tables  9  and  10.  There  was 
incorporated  in  this  grade  8.5  mgm.  of  nitrate.  The  first  extraction  removed 
7.187  mgm.  of  nitrate  in  the  233.46  cc.  of  drainage  (table  10).  Had  the  entire 
250  cc.  of  diluted  nitrate  solution  been  a  homogeneous  mixture,  this  quantity 
of  solution  could  have  contained  only  7.695  mgm.  of  the  original  8,5  mgm. 
incorporated. 

In  the  second  extraction  of  this  grade,  0.48  mgm.  of  the  1.313  mgm.  actually 
remaining  in  the  quartz,  was  removed  in  the  232.85  cc.  of  drainage.  Had  this 
second  solution  been  homogeneous,  0.515  mgm.  of  nitrate  would  have  been 
recovered,  which  still  leaves  0.798^  mgm.  of  nitrate  to  be  accounted  for. 

How  shall  we  account  for  the  apparent  failure  of  0.805  mgm.  of  nitrate  to 
go  into  solution  in  the  first,  and  0.798  mgm.  in  second  extraction?  To  the 
writer  there  seems  but  one  answer  to  this  question,  that  of  King  (46).  When 
the  nitrate  solution  came  in  contact  with  the  quartz  particles,  a  definite  attrac- 
tion due  to  the  force  of  adhesion  was  set  up.  The  quantity  of  the  more  con- 
centrated solution  added  was  greater  than  the  sand  could  hold  by  adsorption, 
so  that  when  the  distilled  water  was  supplied  the  nitrate  solution  held  me- 
chanically only,  formed  a  homogeneous  mixture  with  the  water  when  stirred. 
The  16.54  cc.  of  solution  remaining  in  the  quartz  after  the  first  extraction,  if 
of  the  same  composition  as  the  233.46  cc.  removed,  would  have  contained 
0.508  mgm.  of  nitrate.  This  is  0.028  mgm.  in  excess  of  the  0.48  mgm.  actually 
removed  in  the  second  extraction,  or,  0.007  mgm.  less  than  would  have  been 
contained  in  the  250  cc.  of  solution  had  it  been  of  the  same  composition  as 
that  draining  from  the  sand. 

Since  the  dilution  is  so  much  greater  in  the  second  extraction,  it  may  be 
expected  that  the  outer  part  of  the  film,  less  strongly  adhering  to  the  particles 
would  tend  to  form  a  homogeneous  mixture  with  the  water,  this  together  with 
the  nitrate  solution  held  mechanically  only,  and  that  coming  by  diffusion  from 
the  strongly  held  film,  furnishes  the  whole  of  the  nitrate  removed  in  the  second 
extraction.  King's  data,  table  A  (p.  177),  shows  that  after  six  extractions 
the  nitrate  recovered  is  that  coming  from  the  strongly  adhering  film  by 
diffusion. 

Five  months  after  the  two  extractions  were  made,  the  air-dry  quartz  samples 
which  had  stood  in  the  laboratory  in  beakers  covered  with  paper  were  them- 
selves treated  with  phenoldisulfonic  acid  and  nitrates  determined  in  the  usual 
way.  The  nitrate  so  determined  is  shown  as  milligrams  and  per  cent  of  the 
total  in  the  latter  part  of  table  10.  In  no  case  did  the  samples  which  had  been 
heated  in  the  previous  extractions  show  the  presence  of  nitrates,  while  all 

•8.5  mgm.  total;  actually  removed  by  first  extraction,  7.187  mgm.,  or  1.313  mgm. 
remained;  1.313  —  0.515  =  0.798  mgm. 


EFFECT   OF  DRYING    SOILS   ON  WATER-SOLUBLE  CONSTITUENTS  207 

unheated  samples  contained  considerable  quantities  of  nitrates.  No  claim 
is  made  that  the  conditions  under  which  these  had  been  stored  are  such  that 
the  nitrate  now  recovered,  together  with  that  previously  removed,  should 
equal  100  per  cent  of  the  original  quantity  of  nitrate  used.  However,  it  is 
notable  that  in  all  except  the  fine  sand  size  the  total  recovery  is  nearly  100 
per  cent. 

These  data  are  not  in  accord  with  those  of  Noyes  (71)  who  reports  all  nitrate 
recovered  in  one  extraction  nor  with  those  of  Bouyoucos  (6),  published  since 
the  above  was  written,  who  states  that  the  soil  solution  is  less  concentrated 
at  the  immediate  surface  of  the  particles. 

Under  the  conditions  of  this  experiment,  not  all  of  the  nitrate  added  to 
pure  quartz  nor  to  a  soil  containing  but  a  faint  trace  of  nitrate  (white  silt 
loam,  table  6),  was  recovered  in  one  extraction  nor  even  in  two  extractions. 
WTiile  the  data  here  reported  are  entirely  too  meager  to  warrant  definite 
conclusions,  yet  it  is  significant  that  extracting  the  quartz  itself  brings  the 
nitrate  recovered  so  near  100  per  cent  of  the  total  added. 

This  work  corroborates  in  ever}amportant  detail  that  of  King  (46)  and  though 
these  data  are  meager  they  indicate  clearly  that  with  soils  containing  a  moder- 
ately low  percentage  of  capillary  moisture,  at,  or  slightly  below  optimum,  much 
of  the  soluble  salts  are  held  in  this  film  moisture.  This  film  adheres  so  strongly 
to  the  particle  that  much  of  the  soluble  material  it  contains  is  given  up  to  water 
on  extraction  by  diffusion  only  and  this  explains,  in  part,  the  effect  of  air- 
drying.  WTien  the  capillary  moisture  is  lost  the  salts  are  left  as  minute  crys- 
tals  on  the  soil  particles,  and  it  is  clear  that  quickly  washing  with  water  will 
bring  these  salts  into  solution  so  as  to  give  a  more  homogeneous  solution  than 
can  be  obtained  by  washing  a  moderately  moist  soil  in  the  same  way. 

When  a  soil  is  oven-dried  we  get  all  of  the  effect  of  air-drying  just  discussed, 
together  with  several  additional  effects.  Heating  at  105°C.  coagulates  the 
colloids.  This  the  oven-dry  samples  showed  very  clearly,  on  working  them 
with  a  pestle  in  the  mortar.  With  the  heavier  soils  much  difficulty  was  en- 
countered in  making  a  "thin  paste,"  as  the  soil  adhered  so  tightly  to  both  the 
pestle  and  the  mortar.  After  heating,  there  was  no  tenacity  whatever,  a 
hesLvy  silt  or  clay  loam  working  as  easily  as  did  fine  sandy  loam.  This  action 
on  the  colloidal  matter  would  enable  the  water  to  come  into  more  intimate 
contact  with  the  material  which  exposes  the  major  part  of  the  total  surface 
of  the  soil.  As  already  shown,  Hulett  and  Allen  (37),  the  particles  of  colloidal 
size  are  more  soluble  than  larger  ones.  This  effect  on  colloids  is  undoubtedly 
an  important  factor,  and  helps  explain  higher  solubility  in  the  soils  with 
smallest  particles. 

Authors  cited  above  hold  that  heating  alters  organic  as  well  as  inorganic 
materials  in  the  soil,  rendering  them  more  soluble.  \Miile  the  physical  factor 
in  sands  and  silt  loam  has  been  sho^\^l  to  explain  in  part  the  increased  recover)' 
of  salts  due  to  heating,  it  seems  to  the  writer  that  the  effect  on  colloids  and  the 
well-known  effect  of  heat  in  increasing  the  solubility  of  some  minerals  and 
organic  matter  also  are  important  factors. 


208  A.   F.    GUSTAFSON 

SUMMARY 

1.  Oven-drying  increased  to  a  marked^degree  the  quantity  of  water-soluble 
material  removed  from  soil  by  1 : 5  extraction  with  distilled  water. 
1^'  2.  Air-drying  swamp  soils  increased  the  water-soluble  material  and  oven- 
drying  this  air-dried  soil  brought  about  a  still  further  increase. 

3.  Storing  soils  for  9  weeks  at  8  to  12°C.  in  open  jars  (in  which  water  evapo- 
rated was  restored  each  week)  or  m  sealed  tubes  in  its  original  condition  did 
not  markedly  affect  the  total  soluble  material.  Nitrification  occurred  in  the 
open  jars,  while  nitrates  decreased,  as  a  rule,  in  the  sealed  tubes, 

4.  Keeping  soil  at  room  temperature  and  optimum  moisture  content  for  9 
weeks  did  not  materially  affect  the  amount  of  soluble  material,  but  there  was 
a  slight  increase  in  all  soils  except  white  silt  loam.  Keeping  these  soils  sat- 
urated at  the  same  temperature,  greatly  increased  the  soluble  material.  In 
the  first  case  nitrification  was  active  while  in  the  latter,  denitrification  was 
complete. 

5.  Oven-drying  decreased  the  nitrate-content  of  these  soils. 

6.  Wlien  potassium  nitrate  in  two  concentrations  was  added  to  four  grades 
of  quartz,  it  was  not  wholly  recovered  in  one,  or  even  two  1:5  extractions. 
From  the  more  dilute  solution  67  to  80  per  cent  of  the  nitrate  were  recovered 
in  one  extraction,  while  from  the  more  concentrated,  77  to  95  per  cent  were 
recovered. 

7.  When  potassium  nitrate  in  a  dish  is  heated  in  an  oven  at  105°C.  for  8 
hours,  after  being  evaporated  to  dryness,  a  distinct  loss  of  nitrate  occurs. 

GENERAL  CONCLUSIONS 

The  literature  cited  and  the  experimental  work  here  reported  both  bring  out 
one  important  point.  They  show  the  effect  of  drying  at  room  temperature, 
and  heating  in  an  oven  at  slightly  above  the  boiling  point,  and  in  the  autoclave 
at  various  pressures  and  temperatures.  In  general,  the  quantity  of  soluble 
inorganic  constituents  and  organic  matter  is  increased,  while  temperatures 
above  100°C.  reduce  the  quantity  of  nitrates.  These  facts  indicate  that  in 
planning  soil  biology  studies,  pot-culture  or  other  greenhouse  fertility  inves- 
tigations, the  soils  used  should  be  kept  under  conditions  strictly  comparable 
as  to  aeration,  moisture  content  and  temperature  in  order  to  avoid  the  intro- 
duction of  uncontrolled  factors  which  might  lead  to  erroneous  conclusions. 

REFERENCES 

(1)  AiTKEN,  J.     1910    The  fertilizing  influence  of  sunlight.    In  Nature  (London),  v.  83, 

p.  37. 

(2)  Allen,  E.  R.,  and  Bonazzi,  A.     1915    On  nitrification.    Ohio  Agr.  Exp.  Sta.  Tech. 

Bui.  7,  p.  37. 

(3)  Beaxjtviont,  a.  B.     1919    Studies  in  the  reversibility  of  the  colloidal  condition  of 

soils.    N.  Y.  (Cornell)  Agr.  Exp.  Sta.  Mem.  21,  p.  479-524. 


EFFECT   OF  DRYING   SOILS   ON   WATER-SO LU RLE  CONSTITUENTS  209 

(4)  BONSTEEL,  J.  A.,  FiPPiN,  E.  O.  AND  CARTER,  W.  T.     1905     Soil  survey  of  Tompkins 

County,  N.  Y,     U.  S.  Dcpt.  Apr.,  Field  Operations  Bur.  Soils,  7th  Kpt.,  p.  29. 

(5)  BouYOUCOs,  G.  J.     1915    Tlic  freezing  point  method  as  a  new  means  of  measuring 

the  concentration  of  the  soil  solution  directly  in  the  soil.     Mich.  Agr.  Exp.  Sta. 
Tech.  Bui.  24,  p.  31-32. 

(6)  BouYOUCOS,  G.  J.     1921     The  concentration  of  the  soil  solution  around  the  soil  i\ir- 

ticles.    In  Soil  Sci.,  v.  11,  p.  131-138. 

(7)  Buck,  E,     1915    Rdb:  A  unique  system  of  cultivating  rice  in  western  India.    In 

Internat.  Inst.  Agr.  (Rome)  Mo.  Bui.  Agr.  Intel,  and  Plant  Diseases,  v.  6, 
p.  1111-1117.    Abs.  in  Exp.  Sta.  Rec.  (1916),  v.  35,  p.  138. 

(8)  BuDDiN,  Walter     1914    Note  on  the  increased  nitrate  content  of  soil  subjected  to 

temporary  drying  in  the  laboratory.     In  Jour.  Agr.  Sci.,  v.  6,  p.  452-455. 

(9)  Card,  F.  W.,  and  Blake,  M.  A.     1905    Report  of  the  Horticultural  Division.    In 

R.  I.  Agr.  Exp.  Sta.  Ann.  Rpt.  1905,  p.  197-219. 

(10)  Christensen,  H.  R.     1917    Experiments  in  methods  for  determining  reaction  of 

soils.    In  Soil  Sci.,  v.  4,  p.  115-178. 

(11)  Coffey,  G.  N.  and  Party    1902     Soil  Survey  of  St.  Clair  County,  111.    U.  S.  Dept. 

Agr.,  Field  Operations  Bur.  Soils,  4th  Rpt.,  p.  85. 

(12)  Coffey,  G.N.,  Ely,  C.W.,  Mann,  C.  J.,  etal.    1903    Soil  Survey  of  McLean  County, 

111.    U.  S.  Dept.  Agr.,  Field  Operations  Bur.  Soils,  5th  Rpt.,  p.  785. 

(13)  Coffey,  G.  N.,  Ely,  C.  W.,  et  al.     1903    Soil  Survey  of  Sangamon  County,  111. 

U.  S.  Dept.  Agr.,  Field  Operations  Bur.  Soils,  5th  Rpt.,  p.  710-712. 

(14)  Coleman,  D.  A.,  Lint,  H.  C,  and  Kopeloff,  N.     1916    Can  soil  be  sterilized  with- 

out radical  alteration?    In  Soil  Sci.,  v.  1,  p.  259-274. 

(15)  Connor,  S.  D.     1916    Acid  soils  and  the  effect  of  acid  phosphate  and  other  ferti- 

lizers upon  them.    In  Jour.  Indus.  Engin.  Chem.,  v.  8,  p.  35-40. 

(16)  Darbishire,  F.  v.,  and  Russell,  E.  J.     1907    Oxidation  in  soils  and  its  relation  to 

productiveness.    In  Jour.  Agr.  Sci.,  v.  2,  p.  305-326. 

(17)  Davy,    Sir    Humphrey    1813     Elements    of    Agricultural    Chemistry.     London. 

p.  299. 

(18)  Deh^rain,  P.  P.,  and  Demoussy,  M.  E.     1896     Sur  Toxydation  de  la  maticre  organic 

du  sol.    In  Ann.  Agron.,  v.  22,  p.  305-337. 

(19)  Dietrich,  Th.     1901     Versuche  uber  den  Einfluss  der  Bodensterilisation  auf  das 

Wachstum  der  in  dem  sterilisierten  Boden  kultivierten  Pflanzen.  In  Jahresb. 
Landw.  Vers.  Marburg,  1901-2,  p.  16.  Abs.  in  Centbl.  Agr.  Chem.  (1903), 
p.  68  and  in  Jour.  Agr.  Sci.  v,  2,  p.  312. 

(20)  Dyer,  B.     1910    Fertilizing  eflfect  of  soil  sterilization.    In  Nature  (Ixjndon),  v.  83, 

p.  96. 

(21)  Ehrenberg,  Paul    1915    Die  Bodenkolloide,  p.  40-201.    Koehler  and  Volckmer, 

Leipzig. 

(22)  Fischer,  Hugo     1912    Vom  Trochnen  des  Bodens.    In  Centbl.  Bakt.  (etc.),  Abt. 

2,  V.  36,  p.  346-349. 

(23)  Fletcher,    P.  1910  The   fertilizing   influence   of   sunlight.    In   Nature    (London), 

V.  83,  p.  156-157. 

(24)  Frank,  B.     1888    Ueber  den  Einfluss,  welchem  des  Steriliziren  des  Erdbodens  auf 

die  Pflanzen-entwickelung  ausubt.  In  Ber.  Deut.  Bot.  Gesell.  (General  versam- 
lungs  Heft),  v.  6,  p.  87-97. 

(25)  Gedroitz,  K.  K.     1909    Influence  of  sterilization  of  the  soil  on  the  growth  of  plants 

on  the  soil.  In  Trudui  Selsk.  Khoz.  Khim.  Lab.  St.  Petersb.,  v.  6,  p.  304^342. 
Abs.  in  Exp.  Sta.  Rec,  v.  23,  p.  221. 

(26)  Hall,  A.  D.     1910    The  fertility  of  the  soil.    In  Science,  n.  s.,  v.'  32,  p.  363-371. 

(27)  Hall,  Thomas  Dennison     1915    A  study  in  wetting  and  drying  the  soil.    Unpub- 

lished thesis,  Cornell  University,  p.  1-30. 


210  A-   ^-   GUSTAFSON 

(28)  Hartwell,  B.  L.,  and  Pember,  F.  R.     1918    The  presence  of  aluminum  as  a  reason 

for  the  difference  in  the  effect  of  so-called  acid  soil  on  barley  and  rye.    In  Soil 
Sci.,  V.  6,  p.  259-280. 

(29)  Hasenbaumer,  J.,  Coppenrath,  E.,  and  Konig,  J.     1905    Einige    neue  Eigen- 

schaften  des  Ackerbodens.    In  Landw.  Vers.  Stat.,  v.  63,  p.  471-478. 

(30)  Hilgard,  E.  W.     1906    Soils,  p.  321-331.    MacMillan,  New  York. 

(31)  Hinson,  W.  M.,  and  Jenkins,  E.  H.     1910    The  management  of  tobacco  seed  beds. 

Conn.  Agr.  Exp.  Sta.  Bui.  166. 

(32)  Hopkins,  C.  G.,  Mosier,  J.  G.,  Pettit,  J.  H.,  and  Fischer,  O.  S.    1913    Bond 

County  soils.    111.  Agr.  Exp.  Sta.  Soil  Rpt.  8,  p.  41-42. 
{33)  Hopkins,  C.  G.,  Mosier,  J.  G.,  Pettit,  J.  H.,  and  Readhim£r,  J.  E.     1912    Sanga- 
mon County  soils.    111.  Agr.  Exp.  Sta.  Soil  Rpt.  4,  p.  21  and  23-34. 

(34)  Hopkins,  C.  G.,  Mosier,  J.  G.,  Van  Alstine,  E.,  and  Garrett,  F.  W.     1913     Pike 

County  soils.    111.  Agr.  Exp.  Sta.  Soil.  Rpt.  11,  p.  33. 

(35)  Hopkins,  C.  G.,  Mosier,  J.  G.,  Van  Alstine,  E.,  AND  Garrett,  F.W.     1918    Cham 

paign  County  soils.     III.  Agr.  Exp.  Sta.  Soil  Rpt.  18,  p.  27. 

(36)  Howard,  A.,  and  Howard,  G.  L.  C.     1909-10    The  fertilizing  influence  of  sunlight. 

In  Nature  (London),  v.  82,  p.  456-457. 

(37)  Hulett,  G.  a.,  and  Allen,  L.  E.     1902    The  solubility  of  gypsum.    In  Jour.  Amer 

Chem.  Soc.  v.  24,  p.  667-679. 

(38)  Johnson,  James.     1916    Preliminary  studies  on  heated  soUs.    7w  Science,  n.  s.,  v.  43, 

p.  434-435. 

(39)  Johnson,  James     1919    The  influence  of  heated  soils  on  seed  germination  and  plant 

growth.    In  Soil  Sci.,  v.  7,  p.  1-104. 

(40)  Kelley,  W.  p.,  and  McGeorge,  W.     1913    The  effect  of  heat  on  Hawaiian  soils. 

Hawaii  Agr.  Exp.  Sta.  Bui.  30,  p.  5-38. 

(41)  Kelley,  W.  P.,  and  Thompson,  A.  R.     1915    The  organic  nitrogen  of  Hawaiian 

soils.    II:  Effects  of  heat  on  soil  nitrogen.    In  Jour.  Amer.  Chem.  Soc,  v,  36, 
p.  434-438. 

(42)  King,  F.  H.     1901     Development  and  distribution  of  nitrates  and  other  soluble  salts 

in  cultivated  soils.    Wis.  Agr.  Exp.  Sta.  Bui.  85,  p.  1-48. 

(43)  King,  F.  H.     1904    Promising  methods  for  the  investigation  of  problems  of  soil  and 

plant  physiology,  and  some  lines  of  investigation  to  which  they  are  adapted.    In 
Proc.  Soc.  Prom.  Agr.  Sci.  (1904),  p.  171-190. 

(44)  King,  F.  H.     1904    Investigations  in  Soil  Management.    Influence  of  Soil  Manage- 

ment upon  the  Water-Soluble  Salts  in  Soils  and  the  Yield  of  Crops,  p.  1-168. 
F.  H.  King,  Madison,  Wis. 

(45)  King,  F.  H.     1905    Investigations  in  soil  management.    U.  S.  Dept.  Agr.  Bur. 

Soils  Bui.  26,  p.  1-124. 

(46)  King,  F.  H.     1909    The  suspension  of  solids  in  fluids  and  the  nature  of  colloids  and 

solutions.    Sep.  from  Trans.    Wis.  Acad.  Sci.,  Arts  and  Letters  16  (1908),  pt.  1, 
p.  275-288.    Abs.  in  Exp.  Sta.  Rec,  v.  21,  p.  19. 

(47)  King,  F.  H.     1911     Farmers  of  Forty  Centuries,  p.  142-143.    F.  H.  King,  Madison, 

Wis. 

(48)  King,  F.  H.     1914    Soil  Management,  p.  297-299.    Orange  Judd  Co.,  New  York. 

(49)  King,   F.  H.,  and  Jeffrey,  J.  A.     1899    The  soluble  salts  of  cultivated    soils. 

Wis.  Agr.  Exp.  Sta.  16th  Ann.  Rpt.,  p.  219-242. 

(50)  King,    F.    H.,    and    Whitson,    A.    R.     1900    Soluble    salts    in    cultivated    soils. 

Wis.  Agr.  Exp.  Sta.,  I7th  Ann.  Rpt.,  p.  204-226. 

(51)  King,  F.  H.,  and  Whitson,  A.  R.     1901     Development  and  distribution  of  nitrates 

in  cultivated  field  soils.    Wis.  Agr.  Exp.  Sta.  18th  Ann.  Rpt.,  p.  210-231. 

(52)  King,  F.  H.,  and  Whitson,  A.  R.     1902     Development  and  distribution  of  nitrates 

in  cultivated  soils.    Wis.  Agr.  Exp.  Sta.  Bui.  93,  p.  1-39. 


EFFECT   OF  DRYING   SOILS   ON  WATER-SOLUBLE  CONSTITUENTS  211 

(53)  Klein,  Millard,  A.     1915    Studies  in  drying  of  soils.    In  Jour.  Amcr.  Soc.  Agron., 

V.  7,  p.  49-77. 

(54)  Koch,  G.  P.     1917    The  effect  of  sterilization  of  soils  by  heat  and  antiseptics  upon 

the  concentration  of  the  soil  solution.    In  Soil  Sci.,  v.  3,  p.  525-530. 

(55)  Koch,  A.,  and  Lijken,  G.     1907     Ueber  die  Veriinderung  eines  leichtcn  Sandbodens 

durch  Sterilisation.    In  Jour.  Landw.,  v.  55,  p.  161-172. 

(56)  KOnig,  J.,  Hasenbaumer,  J.  and  Glenk,  K.     1913    Ueber  die  Anwendung  der 

Dialyse  und  die  Bestimmung  der  Oxydationskraft  fiir  die  Beurteilung  des  Bodcns. 
In  Landw.  Vers.  Stat.,  v.  79-80,  p.  491-534. 

(57)  Kopeloff,  N.,  and  Coleman,  D.  A.     1917    A  review  of  investigations  in  soil  pro- 

tozoa and  soil  sterilization.    In  Soil  Sci.,  v.  3,  no.  3,  p.  197-269. 

(58)  KRtJGER  AND  ScHNEiDEWiND  W.     1899    Ursache  und  Bedeutung  der  Salzpeterzer- 

setzung  im  Boden.    In  Landw.  Jahrb.,  v.  28,  p.  216-252. 

(59)  Leather,  J.  W.     1912    Records  of  drainage  in  India.    Mem.  Dept.  Agr.    India, 

v.  2,  p.  63-140. 

(60)  Llebscher,  G.    1893    Deut.  Landw.  Presse,  no.  94,  p.  976.    Abs.  in  Jour.  Agr. 

Sci.,  V.  2,  p.  311. 

(61)  Lyon,  T.  L.,  and  Bizzell,  J.  A.     1909    Changes  produced  in  soils  by  subjecting 

them  to  steam  under  pressure.    Abs.  in  Jour.  Soc.  Chem.  Indus.,  v.  28,  p,  721. 

(62)  Lyon,  T.  L.,  and  Bizzell,  J.  A.     1910    Effect  of  steam  sterilization  on  the  water- 

soluble  matter  in  soU.    N.  Y.  (Cornell)  Agr.  Exp.  Sta.  Bui.  275,  p.  129-155. 

(63)  Lyon,  T.  L.,  and  Bizzell,  J.  A.     1913    Water-soluble  matter  in  soils  sterilized  and 

reinoculated.    N.  Y.  (Cornell)  Agr.  Exp.  Sta.  Bui.  326,  p.  205-224. 

(64)  Mann,  H.  H.     1908    Report  of  the  agricultural  chemist.    Ann.  Rpt.  Dept.  Agr. 

Bombay,  1908-9,  p.  50-54.    Abs.  in  Exp.  Sta.  Rec,  v.  23,  p.  129. 

(65)  Marbut,  C.  F.,  Bennett,  H.  H.,  Lapham,  J.  E.,  and  Lapham,  M.  H.    1913    Soils 

of  the  United  States.    U.  S.  Dept.  Agr.  Bur.  Soils  Bui.  96. 

(66)  McGeorge,  W.  T.     1915    The  effect  of  partial  sterilization  on  plant  growth.    Hawaii 

Agr.  Exp.  Sta.  Ann.  Rpt.  1915,  p.  37-38. 

(67)  Mellor,  J.  W.     1916    Higher  Mathematics  for  Students  of  Chemistry,  and  Physics, 

p.  521-524  and  528.    Longmans,  New  York. 

(68)  MosLER,  J.  G.,  AND  GusTAFSON,  A.  F.    1917     Soil  Physics  and  Management,  p.  178. 

Lippincott,  Phila. 

(69)  Nagoaka,  1911     Tokio  Col.  of  Agr.  Bui.  4,  p.  265.    Ref.  in  Wis.  Agr.  Exp.  Sta. 

Res.  Bui.  19,  p.  5. 

(70)  NoYES,  H.  A.     1919    The  effect  of  heat  on  the  lime  requirement  of  soils.    In  Jour. 

Amer.  Soc.  Agron,  v.  11,  p.  70-71. 

(71)  NoYES,  H.  A.     1919    Accurate  determination  of  soil  nitrates  by  phenoldisulphonic 

method.    In  Jour.  Indus.  Engin.  Chem.,  v.  11,  p.  213-218. 

(72)  Peterson,  P.  P.    1911    Effect  of  heat  and  oxidation  on  the  phosphorus  of  the  soil. 

Wis.  Agr.  Exp.  Sta.  Res.  Bui.  19,  p.  1-16. 

(73)  Pfieffer,  Th.,  and  Franke,  E.     1896    Beitrag  zur  Frage  der  Verwertung  elemen- 

taren  Stickstoffs  durch  den  Senf.    In  Landw.  Vers.  Stat.,  v.  46,  p.  117-151. 

(74)  Pickering,  S.  U.     1908    Studies  on  germination  and  plant  growth.    In  Jour.  Agr. 

Sci.,  V.  2,  p.  411^34. 

(75)  Pickering,  S.  U.    1908    The  action  of  heat  and  antiseptics  on  soils.    In  Jour.  Agr. 

Sci.,  v.  3,  p.  32-54. 

(76)  Pickering,  S.  U.     1910    Studies  of  the  changes  occurring  in  heated  soils.    In  Jour. 

Agr.  Sci.,  V.  3,  p.  258-276. 

(77)  Pickering,  S.  U.     1910    Plant  growth  in  heated  soils.    In  Jour.  Agr.  Sci.,  v.  3, 

p.  277-284. 

(78)  Potter,  R.S.,  AND  Snyder,  R.S.    1915    The  determination  ofnitrates  in  soil,    /njour. 

Indus.  Engin.  Chem.,  v.  7,  p.  863-864. 


212  A.   F.    GUSTAFSON 

(79)  Potter,  R.  S.,  and  Snyder,  R.  S.     1916    Extraction  of  nitrates  from  soil.    In  Jour. 

Amer.  Soc.  Agron.,  v.  8,  p.  54-55. 

(80)  Potter,  R.  S.,  and  Snyder,  R.  S.     1918    The  effect  of  heat  on  some  nitrogenous 

constituents  of  soil.    In  Soil  Sci.,  v,  5,  p.  197-212. 

(81)  Rahn,  Otto     1907    Bakteriologische  untersuchungen  iiber  das  Trochnen  des  Bodens. 

in  Centbl.  Bakt.  (etc.),  Abt.  2,  v.  20,  p.  38-61. 

(82)  Richter,  L.     1896    Ueber  die  Veranderung  welcher  Boden  durch  das  sterilizieren 

erleidet.    In  Landw.  Vers.  Stat.,  v.  47,  p.  269-274. 

(83)  Ritter,  G.  a.     1912    Das  Trochnen  der  Erden.    In  Centbl.  Bakt.  (etc.),  Abt.  2, 

V.  33,  p.  116-143. 

(84)  Robinson,  R.  H.     1920    Concerning  the  effect  of  heat  on  the  reaction  between  lime- 

water  and  acid  soils.    In  Soil  Sci.,  v.  9,  p.  151-157. 

(85)  Russell,  E.  J,     1910     The  fertilizing  effect  of  sunlight.    In  Nature   (London), 

V,  83,  p.  6,  249  and  490. 

(86)  Russell,  E.  J.,  and  Hutchinson,  H.  B.     1909    The  effect  of  partial  sterilization  of 

the  soil  on  the  production  of  plant-food.    In  Jour.  Agr.  Sci.,  v.  3,  p.  111-144. 

(87)  Russell,  E.  J.,  and  Petherbredge,  F.  R,     1913    On  the  growth  of  plants  in  par- 

tially sterilized  soils.    In  Jour.  Agr.  Sci.,  v.  5,  p.  248-287. 

(88)  SCHMOEGER,  M.     1893    Ueber  den  Phosphor  im  Moorboden.    In  Ber,  Deut.  Chem. 

Gesel.,  Jahrgang  26,  v.  1,  p.  386-394. 

(89)  ScHREiNER,  Oswald,  and  Failyer,  G.  H.     1906    Colorimetric,  turbidity  and  titra- 

tion methods  used  in  soil  investigations.    U.  S.  Dept.  Agr.  Bur.  Soils  Bui,  31, 
p.  39-41. 

(90)  SCHREiNER,  Oswald,  and  Lathrop,  E.  C.     1912    The  chemistry  of  steam  heated 

soils.    U.  S.  Dept.  Agr.  Bur.  Soils  Bui.  89,  p.  1-37.    Also  in  Jour.  Amer,  Chem. 
Soc,  V.  34,  p.  1142-1259. 

(91)  SCHULZE,  C.     1906    Einige  Beobachtungen  iiber  die  Einwirkung  der  Bodensterilisa- 

tion  auf  die  Entwickelung  der  Pflanzen.    In  Landw.  Vers.  Stat.,  v.  65,  p.  137-147. 

(92)  Seaver,  J.  F.,  and  Clark,  E.  D.     1910    Changes  brought  about  by  heating  of  soils 

and  relation  to  the  growth  of  pyronema  and  other  fungi.    In  Mycologia,  v.  2, 
p.  109-124. 

(93)  Seaver,  F.  J.,  AND  Clark,  E.  D.     1912    Biochemical  studies  on  soils  subjected  to  dry 

heat.    In  Biochem.  Bui.  v.  1,  p.  413-427. 

(94)  Skalskij,  S.     1912    Work  of  the  chemical  laboratory  of  the    Ploti    Experiment 

Station,  1912.    In  Godichnyi  Otchet  Ploti  Selsk.  Khoz.  Opytn  Stanstii,  v.  18, 
p.  133-227.    Ahs.  in  Exp.  Sta.  Rec,  v.  30,  p.  216,  349-380. 

(95)  Skalskij,  S.     1916    Method  of  sterilizing  and  chloroforming  soil  used  in  studying 

chernozem.    In  luzh.  Russ.  Selsk.  Khoz.  Gaz.,  1916,  no.  1,  p.  7-8;  no.  2,  p.  6-7; 
no.  5,  p.  5-10.    Ahs.  in  Exp.  Sta.  Rec,  v.  38,  17-18. 

(96)  Stewart,  G.  R.     1918    The  effect  of  season  and  crop  growth  on  soil  extract.    In 

Jour.  Agr.  Res.,  v.  12,  p.  311-368. 

(97)  Stone,  G.  E.,  Lodge,  O.  A.,  ant)  Smith,  R.  G.    1912    Influence  of  soil  decoctions 

from  sterilized  and  unsterilized  soils  upon  bacterial  growths.    Mass.  Agr.  Exp. 
Sta.  24th  Ann.  Rpt.,  p.  126-134. 

(98)  Stone,  G.  E.,  and  Monohan,  N.  F.     1906    Report  of  the  Botanist.  Mass.  (Hatch) 

Agr.  Exp.  Sta.  18th  Ann.  Rpt.,  p.  125-134. 

(99)  Stoot,  G.  E.,  and  Smith,  R.  G.     1898    Nematode  worms.     Mass.  (Hatch)  Agr. 

Exp.  Sta.  Bui.  55,  p.  1-67. 

(100)  Tacke,  B.     1897     Die  Arbeiten  im  Laboratorium  der  Station  in  Bremen  und  die 

Feld,  und  Wiesenversuche  in  den  bremischen  Mooren.    In  Centbl.  Agr.  Chem,, 
v,  26,  p.  366-382. 

(101)  Tacke,  Br.,  and  Immendorf,  H.     1898    Untersuchungen  iiber  die  Phosphorver- 

bindungen  des  Moorbodens.    In  Landw.  Jahrb.,  Suppl.,  v.  274,  p.  303-348. 


EFFECT   OF   DR\1NG   SOILS   ON   WATER-SOLUBLE  CONSTITUENTS  213 

(102)  Warington,  R.     1882    On  tlie  determination  of  nitric  acid  in  soils.    In  Jour.  Chem. 

Soc.  (London),  Trans.,  v.  41,  p.  351-360. 

(103)  Whitney,  M.,  and  Cameron,  F.  K.     1903    The  chemistry  of  the  soil  as  related 

to  crop  production.     U.  S.  Dept.  Agr.  Bur.  Soils  Bui.  22,  p.  1-71. 

(104)  Whitson,  a.  R.     1903    Studies  in  the  development  and  distribution  of  nitrates  and 

total  water-soluble  salts  in  field  soils.    Wis.  Agr.  E.xp.  Sta.  20th  Ann.  Rpt., 
p.  339-344. 

(105)  Wilson,  A.     1915     Changes  in  soil  brought  about  by  heating.    In  Sci.  Proc.  Roy. 

Dublin  Soc,  v.  14  (n.  s.,  no.  38),  p.  513-520. 

(106)  Wilson,  G.  W.     1914    Studies  of  plant  growth  in  heated  soils.    In  Biochem.  Bui., 

V,  3,  p.  202-209. 


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